I've been bad

[Whatigot]

I've seen some really solid, open 'scapes by people who drill a hole right into the rock and use PVC as a structure from drilled rock to drilled rock...

If you do it eright, you won't even be able to see the PVC and you can still have some open spaces...

I think aquascaping is so trial and error though, you gotta really mess around to find a way of having your rocks just "fit" and still leave you with enough open space for you to enjoy your fish.