Telescope Reviews: Focal Reducer & Chip Distance

I have a question that I'm hoping some of our imaging and optical gurus can help me with.

I have 2 separate scopes I use for imaging, ZS66 and a CPC925. I have a FR for each of these. The W/O 0.8x for the ZS66 and the Celestron 6.3 for my CPC.

2 weeks ago, I bought a new toy - one of the Orion 2" filter wheels.

Now comes the tricky part. I've finally gotten time tonight to sit down with it to see how I can mate it up with my Canon XSI and my 2 scopes.

Under "normal" operations, if there is such a thing, I have the correct (or close to it) spacing between the FR and the CCD. Now with the filter wheel in the mix, the only way I can see to mate all this up with the parts/pieces I have is to place the FR in front of the wheel. This is going to add ~20mm of distance between the FR and the CCD.

From what I can tell, I think this is going to increase the effect of the FR. If that's true, won't it also increase any vignetting that I may already have?

Anyone know of a place that sells a short (like 1/4" added to the train) T-Male->SCT Male adapter? I think that may help solve the problem long term.

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Celestron CPC925
Celestron F/6.3 Focal Reducer
Feathertouch Focuser
Losmandy Counterbalance
William Optics SZ66 SD APO w/ ADM Rings
William Optics 0.8 Focal Reducer
Canon XSi - Self Modded
Orion StarShoot Autoguider
Philips SPC900
Orion 2" Filter Wheel
Hardin 12" F/5 Dob