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Matt, when you are using eyepieces, you look at a focussed image which is at the focal length from the primary mirror. It is basically somewhere inside the focusser draw tube, sort of below or just inside the bottom of your eyepiece. When you want to photograph, you want that focussed image to be at the CCD of the camera. However you mount your camera, that CCD will normally be some distance above the top of the focusser draw tube. Houston, we have a problem! Hence why people shorten the tube, meaning that the focal point moves further away from the central axis of the tube - ie. further out through the focusser draw tube. One issue that may arise is that the secondary mirror is no longer big enough to capture all the converging light cone and turn it 90 deg - you may lose some of the available light.
Options that may work - you have to experiment. 1) Use the primary collimating screws to push the primary mirror further up the tube - maybe even replace them with longer screws. You might get into all sorts of issues around the support springs. 2) Replace the standard focusser with a low profile focusser (GSO make them and Bintel/Andrews sell them - or ask here in IceTrades for a second-hand). Both those might get you there, depending on your camera and how you mount it.
You can still use the scope for eyepiece observing, but will have to add an extension tube to the top of the focusser draw tube.
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