Trevor, I have been working on my seats this afternoon and have come up with an idea which may provide quick removal for floor sleeping below, which no doubt is preferable to on top.
Replace the bolts with suitably rounded stainless location pins [there are several ways to hold these in position in the wooden seats, with corresponding female locaters [tophat shaped] fixed to the thwart. Fix slightly larger hatch cover type clips under the thwart and thats it. What do you think ! Pete 7059