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Lee,
I would cut the tube only as a last resort. The first things to try are what you already tried, removing the T ring etc to get the body as close to the focuser as you can. I used a lower focuser as well, but this is a cost which you may not want or require. Try longer collimation screws as well, shifting the primary towards the secondary and sometimes this can be all that is needed. I would aim to have infinity focus with the DSLR, and about 2 mm's in focus just in case. Any more is wasted.
Lastly, how does the primary cell attach? Is it with three screws/bolts into the tube, or an annulus ring with numerous screws? If three screws/bolts you could just bore three new ones a little closer, and "patch" the existing ones. If the annulus, at least your rough cut will be hidden.
Gary
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