Focal reducer for Mak telescope

[dark star]

I thought I would post this in the imaging section as well, I already posted in the equipment help section.

I would like to get a 2 inch focal reducer for my Intes MK66 150mm f/12 Mak telescope to use with a Canon 20D DSLR.

However, it needs 70mm of back focus and I don't see of any way to get this. Low profile visual back? At the moment the visual back, T2-EOS adaptor and 1.25 to 2 inch adaptor add up to around 80mm.

Is anyone using a focal reducer with a Mak for imaging, and if so how did you get round the back focus problem?

I know very little about imaging, but have started photographing spectra of stars using a spectroscopic grating. Thanks in advance for any advice.