I use it with my SL66 and right now there is a Wista Field mounted on it. It definitely works well with the SL66 and lenses between 50mm and 250mm, as long as you do not get confused with the four controls (general lock, tilt lock pan lock and friction).
The Wista is a loan. I did not have the chance to go out with it yet but it seems to be ok, at least with the 210mm attached.
Thanks for the info. I'd be interested to hear how it works out with the Wista after a little field testing.