I don't shoot a whole lot of indoor on-camera flash shots either, but can tell you that the TTL metering on my F3 works well with my old SB-16 flash. I've also used a Metz CL-1 off camera with the flash on auto (camera at 1/80 flash sync, fixed aperture) with fine results with the F3.

Perhaps this is stating the obvious, but why not just run a test roll with the SB-800 before finding out the hard way (ie., after the wedding!) that there's a problem?

Best, Graham