Brian,
I use a wooden surveyors tripod. (David White). I initially used a 3047 Bogen head and it worked well for my 4X5 and 8X10. With the 12X20, the 3047 head was too light. I found a used Majestic gear head (1901) on ebay and had a machine shop make an aluminum adapter to convert the 1 7/8 post head on the Majestic to a 3/8 screw mount (cost $27.00 for the adapter). I just got it put together this morning and it is rock solid. The head is rated at 35 lbs. the tripod at least that much. This is my poormans attempt at a Reis. Probably got into it for about a third of what a Reis would have cost.