I've used an pacific laser system 1/4-20 adaptor in the past to attach cameras or tripod heads to surveying tripods, but it'd be nice to attach the big cameras right to the tripod for maximum solidness.
The 5/8-11 thread is also shared with some angle grinders. I bought a bosch angle grinder flange which is 5/8-11 and it fits the tripod well.
Next thing is to drill another hole in my 8x10's sliding tripod block and countersink this into the top of the hole. Other people could use this with their homemade adaptors.