In the 4500, the wood around the windows
is held in place by the sandwich made by the plywood,the window frames and the fiberglass trailer shell.
In this case the trailer shell is the "Meat" and the wood and window frames are the "Bread"
When I replacd the wood in mine I just pulled the windows
out,pulled back the ensolite rubber and what was left of the plywood came right out.
Using the old wood to reproduce the angle needed and cutting the wood to length I then just glued it to the ensolite on the inside and also to the inside of the shell where it goes.
I used a 3M adhesive and it worked great to hold it in place until I could fasten everything.
Then I re-installed the window using butyl rubber sealant and used stainless steel screws to attach the window to the new wood thru the shell.
It is strong enough now to hang and sleep on if you wanted to,oh wait you do want to!
As for attaching to fresh spots,I am the guy who asked that question in the thread Brian sited and I have not decided yet what I will do.
I know I would feel a lot safer bolting thru the shell and into wood than just glueing anything either above my head or for sleeping but I can certainly accept that there are safe ways to approach it with or without fiberglass and resin as part of it.
I am still trying to decide.