I'm a big fan of the driftwood, you just need to season it like crazy. I like to put the rocks around driftwood pieces to provide support.
Do you have a 1X4 piece of egg crate. Its a pain, but idealy you want to place the egg crate first, then rocks then substrate. It makes vacuuming tough and you really can't rearange the base rocks, but its the best way to distrubute the rock weight.