Hi Paul,
Seems to be quite an issue. I don't know anything about your system but these questions come to mind.
1. Is the ASA flattener the only option? Maybe there is a different option consuming less backfocus.*
2. Is there a thinner option for the rotator?
3. Can you contact the scope manufacturer for their take on your situation?
Best of luck with this!
Peter
*edit: actually can you explain the 108mm figure? Is that the required distance from the flange of the flattener to the CCD chip? If so then what you are saying is that the camera will consume ca 62 mm of that distance leaving only 46 mm for the Atlas focuser (which wouldn't fit). Guess I'm confused.
Edit #2: What about this? I think it claims to be .85" back focus 2.9" aperture.
http://www.observatory.org/rotator.htm