I think your idea of the boards to the ceiling, then suspending the cables from the boards, is probably as good as any. If necessary, you could hang a rod from the ceiling and attach your cables to that. I sort of did that to hang a hood over my last tank, except the rod went into parallel walls instead of the ceiling.

If you want to avoid any drilling into the ceiling and you have access to the back of your stand, you can atttach "posts" to the back of your stand which extend up, then put brackets on thos to hang a rod and suspend your fixtures from that. That's a lot of work, though.

Matt