Scott, few of us are
building astro cameras but until that is finished I am just playing around with my DSLR and the filters. The reason I cannot use the filter wheel is that my flattener requires 55mm distance to the sensor while Canon DSLRs have 44mm distance of the sensor to flange. The filter wheel is thicker than 11mm so that rules it out (or the flattener).
I do have a DSLR filter holder but the rings on these filters are too thick and don't fit. I will 3D print a holder but didn't get around to doing it yet. This will bring the distance of the filter to sensor to about 50mm, hopefully this will solve the problem or at least help a bit.