Well, Plan A is done. We do not have a heat vent under the shower in our Rockwood Ultra lite 2604, so I could remove the access panel and see everything clearly.
The shower in our trailer sits on a 5/8" plywood shelf that is cut to fit the bottom of the shower allowing for the drain in the middle. On top of the plywood is a 1/2" thick pc of foam like the foam used in making formed packing trays. This is the problem because as you use the shower, this foam compresses and creates a gap between the bottom of the shower and the plywood shelf and this is where the flexing comes from.
My fix was to make a bridge that fits across the front of the shelf with a large surface of Velcro to keep the shower bottom snug against the remaining foam/plywood shelf. The Velcro keeps the shower bottom from flexing up.
I do have pictures but am not posting here. If you would like to see them, PM me with your e-mail address and I will send them to you.
The bottom line is that the flexing does not appear to be a structural problem, it is just annoying.
DadH
Trailerless but still have the spirit
2013 Rockwood Ultra Lite 2604 - new family
2007 Rockwood ROO HTT - new family
2003 Ford F-150
4 doggies - We support Adopt/Rescue.
Sam, you were the best!
Cubbie, Foxy, Biscuit and Lily - all rescues!