Howard,
You are correct in your physics but (I think) mistaken in your mechanics. On my tramp (stock hobie I believe) the flared opening in the side-rail does not even contact the trampoline whatsoever when it (the flared portion) is oriented to the rear of the boat(contrary to the manual). So, regardless of the forces being greater back there (true) it makes no difference at the stern at all in terms of trampoline support. It only changes things up front. Because if the flared portion is oriented up there, the tramp does have contact with it and of course it provides no support along those several inches.
Dave