You may want to PM DramaQueen. She has a big moved planned, so she might be able to give you info about this.
I've done shorter trips with my guys, and used the same method that Ayala described. I also put a half-filled bottle of water into the cup holder, so that I could watch it and monitor what was happening with the water. I figured that if the water in the bottle didn't slosh, then the water in their cups should be pretty much OK, too.
I'd say that the fish weren't thrilled with the whole thing, but we arrived with everyone intact.