I have been reading this post for a few days and wondering if i can offer anything.
First thing i was thinking was the only way to find out what everything weights, is take it to the scales. The second, is the only way to find out about any problems with adding loads, is to drive it.
I read you were going to weigh it without the Scion. that's a good idea and a good data point to have. But if you will be traveling with it loaded, you also need that weight also. Having the Scion on board will most likely change the way the RV tracks, possibly dramatically.
I also looked at the weight of your Cyclone. Interesting that the axles can handle the entire GVWR of 18,000#. That would be bad of course because you need pin weight to properly balance the trailer load. You could just imagine what would happen if all the weight was on the axles and you where to accelerate or brake or go over rough road and impose a rapid change in truck bed load or even lift the truck off the road going over rough roads. The DRW ram has several thousand more pounds of load capability on the rear axle than it's rated payload and can handle any extra weight you would get when braking with max pin weight. I'm new at pulling a 5th wheel, but it didn't take long to figure out i wanted to load as much pin weight as i could without exceeding the truck's payload spec. That might take more than one trip to the scales and redistributing loads.
There had been some problems with frame cracks on the early Lippert frames near the pin box, but i think that was sorted out and i don't see any specs on max pin weights.
The best place for the Scion's extra weight would be over the trailer axles. That's not possible of course. You can speculate all you want about what your pin weight is, but the only way to do that is on a scale. You would need to weight with everything loaded including the truck with passengers and a full tank of fuel. You have concerns about adding the Scion, getting weights with and without the Scion would be helpful. You would also have to un-hook and re-weight just the Ram 3500 and passengers to find out your pin weight, and the GVWR of the truck and GVWR of the Cyclone.
My wife and i just had that discussion the other day about GVWR and GCVW and first thing she said was "everyone she talked too is very confused". Or i should say i had that discussion.......and she tolerated it.
I am too whenever someone presents a good enough question that i have to look at my notes i took reading "Title 49 U.S.C
First thing i saw was it was written for "commercial transportation".
Second thing i noticed, was it was it's purpose was to make uniform, our State traffic laws. It basically made your driver's license from whatever state you reside in, legal in all states. And doing so, the States were then able to have some of that federal gas tax money come back to them for road repairs.
This was one of the greatest laws thought out and written as far as it really does protect and preserve out health, safety and welfare....enforces the liberty we RV's have.....and hopefully not not the last.
I can go on for some time with exceptions including state and local regs, and mis-interpretations.
But it is the standard to how to spec vehicle weights and what all 50 States use.
What you have to be concerned with is what is printed on your RV and inside the truck door. My Cyclone has individual axle ratings and a total trailer GVWR weight. My 2010 Ram 3500 HD has individual axle ratings and also GVWR weight. No GCWR which i think some of the newer trucks have.
This is where it begins to get complicated. There's road weight limits, and commercial weight limits that require a commercial driver's license, if your "in commerce". These are GCWR. The truck and trailer weight combined. I might be missing something, but i think these are the extent of what your truck can tow. At least on my long bed 2010 3500 HD Ram, there's no listed GCWR, but in my owner's manual, there is an estimated weight. Does that mean if i want my transmission replaced under warranty and i own up to towing a 40,000# trailer my claim will be denied........probably.
Does that mean if I'm at my manufacture's GCWR driving in the rain, at night in the hills on a two lane road with no shoulder at the posted speed limit I'm unsafe...........probably.
Does that mean i can pass commercial truckers on a long hill at 50 mph on a divided interstate highway safely when they are in low gear going 20 mph........probably.
These are all important limits and should not be exceeded at the risk of a fine and possibly inpoundment. But if you are non-commercial, and don't have to weight at truck weight stations on the interstate highways, you may never have to be concerned with a fine. But if you exceed these limits, or your tires are not properly inflated or your equipment is not well maintained, though you don't have a commercial driver's status, you have put yourself at risk as well as others and that falls within normal safe operation of a motor vehicle laws. Because you are not pulling through interstate truck weight stations, it's up to you to self enforce. And any local law enforcement or DOT can cite you in violation if it's obvious your unsafe and within their jurisdiction.
Seat time, and a trip to the scales will answer alot of your questions. It's also good to talk to professional truckers. But i don't concern myself with the actual pages of regulations, I'm way below their limits, and after 6 hours of towing with the trailer wheels within a couple of inches of the fog line, I'm ready to park it after a long day. I don't have any time constraints and I can pick my routes and if the weather is really bad out, i just pop a DVD in and wait until better weather to hit the road again.
There's also a recommended pin weight ratio for tag trailers and 5th wheel RV's. I like to put as much weight in the bed of the truck on the pin as my rated "payload" allows. I don't want to exceed my payload and let the RV control the truck, but the more weight i can put on the truck, the less likely I'll experience any rapid changes in load when i accelerate or brake or hit steep hills, the RV tracks better and the truck feels more secure with all four corners firmly planted and I'm less likely to have any fish tailing which can lead to a very bad day.
so........you also asked a very difficult question about pin weight being part of GVWR. I did a little reading, and i haven't found the exact law that say's A+B=C. I have never had that problem, I've always been way under my trailer/truck load specs.....relatively anyways. But the general consensus is that GVWR is the combination of the pin weight and the axle weights. I think the confusion is with GVW. Which is what your vehicle weights, fully loaded and driven onto the scale. GVWR, gross vehicle rating, is a legal max weight rating your vehicle can weight fully loaded and is the sum of the base curb weight, and options plus cargo. If you refer back to the sticker on the Cyclone, it gives GAWR and GVWR and also what the cargo carrying capacity is and specifically states that should never be exceeded. As far as i know, it's very difficult to have your truck or RV re-certified to a different GVWR. If you were concerned at any time about stresses put on the truck or pin box on the 5th wheel, you could always add an air suspension hitch or pin box or even change the suspension on the Cyclone. But that won't change the sticker values on the truck or RV. Or even unload the Scion and drive that until the towing gets easier.
Just a side note. it could be worse. i read about some of the smaller motor homes built on a van frame that over load with a full tank of fuel and two suit cases.
The Ram 3500 is made to tow......
2010 Ram 3500 HD
2014 Cyclone 3100
G614 Goodyears
Good Sam gps
Timark keyed alike
Xantex 2000 watt inverter "Inverter Service Center"
Blue Sea System toggle source selector
L.E.D. running lights
Quadra Bigfoot levelers
Dexter wet bolts
Boyo wireless backup camera
EMS-HW50C
TST 507RV
Smittybuilt air compressor
Splendide 2100XC
26k Husky hitch
Mor Ryde pin box
Loadlifter 5000 @40psi
6-volt 240 AH batteries