Good ideas, I think the canvas bag idea might work best. There is room in the locker to mount something like that or maybe even a wooden board-holder. It's a little tricky because I also use this locker for access to the engine and other things, so sometimes I have to remove everything in it to make work easier. Any pictures of your board holders would be very helpful!
1980 S2 9.2A (30') in Anacortes, WA
Aux power 13hp Volvo MD7A