Hmmmm...
Long time ago I had that dillema with my maksutov (MTO1000) and Practica VLC3... I solved it by matte glass and home built microscope (mag ~30x) which I placed into plug-in that I sacrificed for the purpose...
In your case, I think Hartmann mask and couple of test exposiures would solve the problem.. Or built-in focus indicator confirmation, but for this you have to have special adapter (a collegue of mine has it for his 350D, he bought it from a guy in Russia and this thing basically acts as a Canon lens, enabling manual focus confirmation functionality.
If you are interested I will ask him on Monday and let you know where he obtained this (it was $50 or so).
in the meantime, have a look at
http://www.bobatkins.com/photography...g_adapter.html
or google a bit :-)