I have a D700 with MB-D10 grip. My tripod is Giottos MH1300 ball head mounted on a Giottos MT-9260 tripod. Whenever I use my new Sigma 150-500mm zoom lens at 500mm, with my tripod mounted to the tripod foot, I have a hard time framing something like the moon. I get everything lined up the way I want them, tighten down the knobs etc. But when I remove my hand from the camera, it moves, throwing my immage off. I've considered replacing my ball head with one of the medium ball heads from RRS. Would that help? Or shoulld I consider another route?