Good Morning Lightweight.
I am over 270 and sat on them, lied down on them, and ,stepped on them, even at the dock. I too was concerned about the stated weight limit. Mine are fairly new, and I saw one post where the straps/buckles came off on someone and they replaced them with something stronger. I don't feel the material will give way.
One thing I have considered was to run webbing straps across the length of the tramp. I am also looking at the spine board HAKA.
What is more bothersome to me is that I can sink the ama if I am far out on the tramp.
Good luck.