In order to tweak my board spacing to get the most use out of the available space, I've got a mix of strategies here. My goals were to keep the fins on as many boards as possible (three of the four stay finned) and have them slide out of the rear board supports sideways so that they could be stacked together so tightly that the footstraps wouldn't clear the rack above if pulled straight back (also the fins don't impede board movement.)
Here's the scheme:
The lowest board is my waveboard (here a Naish 8'5"). It's short (leaving room for a longer board's fin to extend behind it.
Above that is a Bic Techno, which I use for nonplaning freestyle and for teaching. Given its weight I have a hinged support on the right side which reinforces the Techno's horizontal support. I flip the hinged piece down to slide out the wave board.
Above that is the one board that must have it's fin removed (JP Freestyle 109.) I run this board with the largest variety of fins anyway, so it's no particular hassle. This board slides easily slides out sideways.
The top board (a JP 93 Freestyle Wave...my wife's board, which I would never ride without permission) is the only board which slides straight back.
Above the boards is room for four sails (currently 4.7, 5.5, 6.2 and 7.0). Behind the wall support slide two small masts (the rest run behind the large storage boxes on the bottom.) Hidden behind the wave board are my two smallest sails (4.0, 3.4) which are only used when the wave board is out, so that's no inconvenience.