I've used an AP CCDT67 successfully on my RC8:
http://www.iceinspace.com.au/forum/s...d.php?t=100797
My STF-8300M + FW + OAG + Baader 2" nosepiece places the image plane at 85 mm behind the reducer, giving exactly 0.67x reduction, i.e. f/5.36. The image circle is small though - you definitely can't use it with a full frame DSLR.
This reducer consumes a
lot of back focus - with the reducer attached, I only needed one 25 mm extension tube behind my RC8 (with a 2" Moonlite focuser).
There wasn't enough back focus for my adaptive optics unit, so I stopped using the reducer. I might look at using the AP 27TVPH reducer (much more generous with back focus) when I can afford to upgrade to a larger focuser.