[raymo]

O.K Allan and Astro, I've been thinking back and having reread your posts
I sort of think I know what is going on.
Mounting a DSLR is simplicity itself. The tube that an 1.25" eyepiece
slides into is mounted on a flat plate that has a bevel on the side opposite to the eyepiece tube so it can be secured into the collar by the retaining screws on the outside of the collar. The eyepiece tube unscrews from the plate, exposing a male thread on the plate which screws directly into the T-ring on the DSLR. This provides about 12mm of back focus. Just remove the flat plate from the focuser ; with the tube removed just screw the flat plate into the camera's T-ring. Put the camera in place on the focuser, rotate the camera to a convenient position and nip up the securing screws on the outside of the focuser collar.
2" eyepieces or other 2"accessories are not meant to enter the draw tube at all. The aforementioned flat plate that has the tube for 1.25" eyepieces on it is removed from the collar, and the 2" eyepiece adaptor is inserted into the collar, and the securing screws on the outside of the collar nipped up. A 2" eyepiece, or any other 2" accessory can slide in to the full depth of the 2" adaptor. SW have never explained this in their manuals; many people have been confused.
raymo