I'd say approx 98% of our HVX and HV20 users are getting frames centered perfectly. It's not an easy task but because the flip module is decoupled from the adapter, we can adjust for this while keeping sharp image edge to edge. It's impossible to do this with a one piece adapter as you need to move the imaging plane in concert with the 35mm image cone.
The setup video is up at the Cinevate "Video University" which demonstrates. The big difference is that the full width frame (actually larger in many cases at up to 38mm) becomes usable. If you have to keeping zooming in to clear the right or left edge of the imaging plane you end up throwing out usable field of view. Depending on how bad the camera is, this might be as much as 20% loss. This XY alignment issue has been a common complaint with our users and it's the largest reason for the flip still being separate from the base imaging unit.