[RipNC]

Sam,
I built one of these seats for the shower on our trawler and went with SS brackets that folded the seat down (not up). These created a shelf bracket style support from below rather than full cantilever. I secured thru about 1.125" of solid bulkhead and it was very solid. I was leery of the full cantilever option then, when I was doing the install and could see "what's behind the curtain". We voted for the status quo - it was a selling point to us.

PS - inspection of our new rig happens today.