Are you sure you even want a head? If you're going to use it for large format monorail only, an option would be something like this Berlebach tripod:
http://www.berlebach.de/?bereich=details&id=296&sprache=english
Adjust the ball to level the panoramic plate, then mount the camera using the knob underneath the ball to tighten the screw. The camera is kept level during panning. For those occasions when you need to tilt the whole camera, the ball lets you tilt up to 30 degrees in any direction.
Caveat: I haven't used this tripod yet, I've only just ordered it. It's going to carry my Linhof Color monorail 4x5. I figure the simplified construction, relative to a full three-way head, will mean better stability and less vibration.
-tih