I'm going to answer my own question here.
GSO currently have RC scopes with sizes 6", 8", 10" and soon there will be a 12" version and then a 16"
I wanted to know if these larger scopes would support a larger CCD sensor without a field flattener?
After much google searching, I believe the answer is no, they won't.
No matter how big the RC aperture gets, the diffraction limited area stays about the same - (about 14 to 18 mm in diameter)
This is the document that had the answer I was looking for:
link
Check out the last page.
With a field flattener the image circle size jumps to over 40mm.
James