Hi Chris
Here is another possible solution:
http://www.myastroshop.com.au/produc...sp?id=MAS-053A
This is a direct screw in coupling so offers the maximum rigidity as there are no grub screws. A thin collar can be screwed in or out to expose more or less of the 60mm threaded section that screws into the Vixen focuser. This allows you to screw in the DSLR, orientate it correctly and then you can screw in the collar until it jams against the face of the focuser, essentially locking it in place.
If you want to say rotate the DSLR by say 90 degrees, you back off the collar, then screw the 60mm threaded section in another ¼ turn and then re-tighten the collar.
This solution appears to add the minimum extra length to the focus train should you want to add a motorised focuser at some stage.
Cheers
Dennis