I was planning to drive to Deming on Monday to see the trailers at the rally up there since I had respite care for Pam that day. My buddy Darrell offered to make a plywood run that day too and since my little car is hopeless for plywood hauling, we picked up 6 sheets of 3/4" ACX and a couple of sheets of 1/8" Baltic Birch so I can see how it finishes out for later.
I'd made cardboard templates of the front and rear panels before ripping out the old subfloor, so I transferred the rear template to a sheet of plywood, added in the C channel width, and subtracted 1/4" of wiggle room, and cut it out. Went with ACX instead of marine ply since I knew I woud be coating it with epoxy on both sides. I used a router to bullnose the edge on both sides and layed up a 6" piece of fiberglass cloth around that edge, using Rutan BID cloth sourced from Aircraft Spruce and System Three epoxy. That particular cloth I've used before and it goes around corners, like that plywood edge, really well.
I can't think of a better way to seal that vulnerable plywood edge. I'm sure it's overkill since I'm 57 and my trailer is 52--I know what I'm doing will outlast me. Maybe she'll still be around when she is 100, though, and wouldn't that be cool?