Thanks for your reply Steve. That is very, very, very interesting. My 1200D is already IR modded and a cold finger on my 450D is in the works. Your comments stress again that a mono DSLR should be my next step. Not having mono means 1/4 efficiency for H-alpha due to Bayer matrix. Debayering the sensors is not the easiest task though... Glen went through few sensors until he managed to debayer one.
I was actually reading more today and figured out that I cannot even use a wheel with ED80 + flattener + DSLR. The DSLR have large flange-to-sensor distance and with a flattener there is is simply not enough space/focus to fit the filter wheel
Unless I find a way to insert the wheel before the flattener...