Damn Stevant1, you really do think like me

I was thinking about wrapping the steel around the outside edge for the same reason (but hesitated beacuse it's a bigger step in fabrication to crease the steel). If you can do that then you're on your way.
In my drawing the threaded rod extends almost to the centre of the piece, so I don't think the stresses will be very big at all at that point. If you clamp down through the timber section (just either side of the inboard termination bulkhead) then the forces should dissipate quite smoothly into the internal timber framing and then into the ply.
I guess the good thing about this approach is that the design could be changed (the overall platform geometry) whilst retaining the same hardware (the more difficult to make metal pieces and fasteners). The other plus is that your 'timber only' trial platform (if it works) could be turned easily into the final thing with the addition of the metalwork and ply.
Lol, I'm getting excited to see yours in action now
