Just like a chain is only as strong as its weakest link, a camera is only as stable as the most unstable part of its support. You've mentioned the Manfrotto 055B legs - a decent set. The lens mount to the camera is not a point of instability, nor is the tripod ring to lens coupling likely to be one. You mention a pan & tilt head - what brand and model, and what's its rated capacity? The 7D + 70-200mm f/2.8 is a reasonably heavy combo. Also, what (if any) quick-release system?