Yup I definitely agree, a little bit of ingenuity and hard work will go a long way in this hobby. I also know the objective was not to compare, but I was bascially saying it's not entirely apples to apples as the f/4 obviously collects lots more light! I would really like to see how the DSLR fairs on your 10" f/4, that would be very easy to compare to other 10" f/4 images with a CCD.
As for the OAG, I'm surprised you couldnt? Did you not have enough in or back focus? I'd imagine its back focus, if you like you are more than welcome to use my extension tube on my TS9OAG and see if that helps
You shouldnt have any issues with focus on the guidecam once you can move it back far enough, but yes I think the MPCC doesnt have enough backfocus for your set up, especially a DSLR + FW.