One other item of note is that when the corner jacks are pressurized in the least, the TT gets somewhat
sway-backed in the middle. If anyone doesn't believe this is substantial, I invite you to stand on a step ladder and eyeball down one of your rain gutters when the stabs are down in any
tension. From the TT looking level on the wheels alone, my guess is that it is assembled resting on the wheels, because that is the only time mine was straight.
This doesn't seem to be a problem with door closing, or cabinets, but I've never tried to jack the ends to extremes either. The original assumption was that once the weight was off the springs, then the springs no longer suspend the TT and it can't bounce up and down in the least. Wrong. The rubbery frame gives a lot.
Since the frames are flexible, with end jacks, there is always some weight more or less on the springs I suppose, until the tires just about come off the ground.
In our last TT, a 30 footer, any jacking at all immediately caused the rain to run to the center of the roof. If there was little rain, it ran off the roof center and then along the tiny 1/2 inch deep gutters that these units come with and then properly drained off the end spouts. If it was intermediate rain, or more, the gutters overload and rain runs off the sides of each tiny trough... after it mostly runs to the roof middle. Then it runs down the wall, or on the slide roof, depending on TT side tilt.
This "feature" dumped rainwater directly on the slide roof and it did leak until I replaced the slide roof wiper with a taller, robust rubber wiper selected from my RV dealer's unassigned generic stock. Although the TT was level when I set up, it always leaned to the slide thereafter, and I left it, which helped keep rain from running inside the slide attachment wall.
A long term fix on longer campouts was to jack the frame up in the center too, with at least two more jacks. Four were better. One other help was to jack a lower step under light, but solid tension. Most of our objectionable bounce was somebody coming up the cantilevered step assembly and this really helped. Some TT's may have built-in step feet and this should help about the same.
Our long current Class C seems pretty solid as far as bounce, using the spastic hydraulic jacks. Any harder extensive footing, or leveling, will prevent the bathroom door from latching however. These long chassis are like noodles. Motorhomes of all kinds suffer from not being able to tilt fore-and-aft on center axles. Even a moderate off-level pad requires hard jacking and one end or the other may even leave the ground on down-slopes. I know they can because my campmates once allowed the insane auto-jack feature to extend to the degree all four wheels were off the ground while I was trying to sleep in.
If the rear axle is off the ground, the front must be very well blocked from rolling. Ideally one would park the rear axle on very sturdy blocking that will positively resist the duals slipping because that's where all the brakes are. In some cases, I do not have room to bring that much blocking. We have a residential fridge, resistant to tilt, so sometimes we just sleep crooked.