A really useful tripod head is the Bogen/Manfrotto 3047. It's pretty stout, and has a large, hexagonal plate which mates well with the base of the F2. I'm sure loads of people have used that head for their 4x5s in general, as it's a good, solid head with separate three axis controls.
The only problem--although really, with a Sinar F2 (which I have myself) it probably *isn't* a significant issue--is that you can't use the Arca-Swiss quick release system with it, if your tripod for general use employs that system. I personally use my F2 on top of an Arca-Swiss B-1 ballhead with a very nice round plate from Hejnar Photographic that fits the F2 precisely, but sometimes with a bulky 4x5 like the F2, that's *not* the best solution to have it on a ballhead.
I really like the 3047, I used to use a Manfrotto with that on top, and I've thought several times I should just go ahead and get one for use with my F2, although that would probably mean buying another tripod to keep it on as well.