I believe that the biggest concern is the weight and the tire loading. The fresh tanks are generally over the axles, or nearly so. That means pretty much all the 600 or so pounds is going to be on the suspension and tires. If you know that you are still within the tire weight limits, and to a lesser extent the axle limits (our tires can handle 7000# per pair while our axles are rated at 6000#), you should have no problems. If you are over either of those limits, however, I suggest watering up as close to the site as possible and keeping the speed down to avoid heating the tires or stressing the undercarriage. At least, that's what we do and haven't had problems (yet).
Aside note: we have found that a lot of water seems to slosh out of the tank through the vents if we have to go rocking, even slowly, down dirt roads. We have fairly accurate SeeLevel II gauges; when level and we fill to 100% with water coming out of the vents, then trundle down 7 miles of dirt road, we often show only 75-80% remaining at our site. As we maneuver to park the rig, we can see water coming out of the vents above the wheels on both sides, so this is probably the source of the loss. At least it is something to be aware of if your water is going to be critical.
Safe travels!
Tom