After reading this whole thread, I crawled under my 2016 Flagstaff 21FBRS to see how the water tank is installed. I have a 43 gal tank that is sitting on two pieces of 1 1/2" angle iron that is welded to the frame rails. There are two cross member pieces of the same angle iron that look to be at 1/3 and 2/3 of the width tank. The tank, when full, weighs in at 356 lbs.
I always leave home with a full tank, since I almost never plan ahead on where I will be setting up for the first couple of days. It is often just out in the National Forest is some nice quiet spot. I ususally drive home almost completely empty, and I can feel a difference in handling, especially if I haven't been able to find a dump station. The holding tanks are in back, so the weight balance is off. Not too bad, but noticable.
The black covering on my TT is attached to the flooring, so my wiring and plumbing is visible. It looks to be attached down well.
