OK. I finally did my tank fix. First of all, a big thank you to Doug W. for his posts and photos. They really helped me a lot, even though I did it a bit different than he did. Here's how the project went. It took me about five hours, but I had a couple beers on the way.
First I removed the underbelly cover. I cut in between the two water tanks - right between the double beam so that I'd have a solid surface to reattach it to.
Numbers correspond with pictures
1. The first pic is the aft tank - fully drained. This water level is at the level of the pump outlet line in the lower left corner of the tank - so the pump (and drain line) are sucking air at this point.
2. This is a bit further away showing both the aft tank (on the right) and the forward tank (on the left). You can see the remaining water level in both tanks.
3. This next pic is the connector line from the aft tank to the forward tank.
4. This pic is the forward tank with the connector hose going into it from the aft tank. Again, everything is fully drained, but realize that the forward tank has no drain or pump draw. It has to drain back into the aft tank in order for the pump to draw it, so this much water is always in the tank with no way to get at it.
5. The side view of the forward tank.
6. Here's what I did: I pulled the connector hose between the tanks and drained them from there - This is the first time these tanks have been drained since I bought the Cyclone - over a year ago. I measured the amount of water that was left in them at 34 gallons. Fully one-third of my combined tank capacity. I then pulled the metal strap and particle board and dropped the tanks to inspect and finish draining the last of the water.
7. I remounted the tanks and drilled a one inch hole in the center of them - at their lowest point.
8. I purchased two bulkhead blind tank fittings from USI-RV.
9. New drain fittings inserted into holes.
10. Drilled 2.5 inch holes into the center of the particle boards to accommodate the fittings - and then replaced the boards and metal straps.
11. Close up of the fitting.
12. I capped the previous line out to the pump with a 1/2 inch nylon plug.
13. I connected the two bulkhead fittings to a common T-fitting going out to the pump, and another T-fitting for a down-drain.
14. Replaced the underbelly cover with just the down-drain exposed.
Before I replaced the cover, I filled the tanks and then drained them. They drained nearly completely. Just a slight lip inside the tank of the bulkhead fittings keep a very small amount from draining - less than a quart for both tanks I would estimate. Also, no leaks at all. The system works great. I didn't fix the extreme bowing of the tanks and boards, because that is what allows the tanks to drain so well at the low spot. But I'll be sure to never drive with full tanks. These boards could very easily break under that kind of load - just like Doug's did.