Those cross bars bent when myself, my dog and my brother-in-law went out on the seat (140 + 70 + 220 = 430lbs). Not that it wouldn't have bent a little under less stress, but the play in the clamps (which are not tight-fitted but quite loose) and play in the clamp receivers where the conduit seats into is what allowed the crossbar to give a little. It is not going any further. The clamps would have to rotate significantly more and probably stresses applied at near 800 ftlbs to actually bend the conduit.

As for actually standing on the outer seat rail, we haven't done that. While I sit and captain from the rear of the seat (140lb), a friend has sat on the outer rail and holds the trap wire handle (200lb). To stand on it and really leverage your weight I would recommend a thicker diameter tubing or a shorter straight run.

However it's important to understand one thing - I don't use this for racing, the intention was to use for cruising only. The proper materials for water might be stainless steel or aluminum ( aluminum especially for weight - the steel clamps weigh about 5lb x8 =40lbs alone) if for salt water use (you could coat the steel in pvc like is done in dishwashers), and the materials cost x5 at least, so $1000us is not really unreasonable for a tried and true performance-oriented product. This design grew out of the desire to cruise with additional room and wanting a backrest on a 3-4 hour cruise, and 1000us for a lawn chair seemed a little extravagent.

Regardless of that little disclaimer, I'll put together a little more detail of the process involved in the design and manufacture, and show some suggested improvements. I would like this design to be in the public domain so that guys like me who like to build things might also share their ideas.