I have a 4x5 Zone VI (single extension) and hold it up with a Velbon CF tripod and a smalish Slik magnesium alloy ball head. Works for me and I can carry it around.

The 8x10 Kodak 2D goes directly onto a Burlibach wood tripod with a leveling center post. Don't use a ball head or pan head with this rig for simplicity and weight. The center post rotates when unclamped for attaching the camera. The 2D has a sliding tripod block to keep it balanced.

These rigs work pretty well for me.