Hi Paul,
If you have the STD 925 OTA, you might be in the same boat as me but not as bad. If this is the case you may want to look at this adjustable T-Adaptor to solve your issue instead of custom fab $$$.
http://www.sirius-optics.com.au/tele...r-for-sct.html
For me this works well as I have many different size M42 spaces to make the correct backspace for my camera. Another bonus now is I will have clearance between my C8 with reducer and DSLR on the evolution mount.