Hello.
I've been through the process of replacing the pinch welt. I had leaking issues with the bunk ends of my 2010 Rockwood Roo 233S. I still feel it was a design flaw that was corrected in later models but don't hold any hope for Forest River upgrading the bunks.
At first I noticed the pinch welt seemed to be on wrong. The top did not overlap the sides to prevent water going down behind the side pinch welt.
I also noted the frame screws for the bunk ends were protruding up and positioned along the pinch welt. This prevents a tight seal.
I ordered the welt from Forest River direct. The old welt pulls right off and the new presses right on. You could put a sealer or gasket glue on it but I haven't seen the need. I did make sure the new top welt overlaps the sides and used silicone sealant on the corners. I replaced the existing frame screws with flat head stainless steel and used 4200 boat sealant in each hole.
I also noticed the black rubber gasket was loose so I removed that and re-glued with that yellow gasket glue.
I replaced the black pads under the door latch hoping for a tighter seal. After a month the pads retain their shape so I don't think it helped much.
After all this, I still had leaks. Using a hose you could see the water running down the inside. I did some more searching and found a fix by another member. They made a PVC device that prevents water from reaching the top of the bunk ends. I built the same and it has solved my problem. My trailer was covered this winter but uncovered in the spring and has sat during numerous rain storms. The mattress have remained dry with no sign of water.