i tired my C11 with a borrowed 3.3 and my Canon 400D, and can confirm you get a large coma around stars, which you can't focus. All fine with my Celestron 6.3 reducer, i can fit the whole of M42 in my canon.
try the free CCD camera program at
http://www.newastro.com/newastro/boo...camera_app.asp
you can see the results of various telescope/CCD combinations
Domenic