One of the cheapest, stoutest, sturdiest options is an RT90c with something like a Desmond Dlow 55 head. Or skip the Dlow and get the MA-30L head that Duhhh mentioned. It's a little more but also the best style of head to shoot from.
I would try to get in inverted tripod and the MA-30L head. Leofoto probably makes the least expensive inverted tripod besides Fanaue. I was going to buy a Fanaue to test it but the head is built in from what they told me. I worry that the head will wear out over time and then I'll have to tear it apart and hope I can make a flat piece to go in the apex so I can mount an Anvil-30.
Heres a link to the Fanaue. FANAUE Carbon Fiber Inverted Tripod for Rifle With Quick Release Clamp
The BOG legs aren't bad. Probably worth spending a little more though and getting an Innorel, Leofoto, etc to start with.
