You completely misunderstood.
I wasn't talking about A Starlight Instruments rear-mount focuser at all.
I was talking about replacing the actual focusing knob with a 2-speed focus knob, leaving the back of the scope intact at whatever shorter length the visual back yields.
The JMI one, I am sorry, is no longer available:
https://tinyurl.com/ybz4q6m4
The Starlight Instruments one may or may not be available for the Mak:
http://starlightinstruments.com/stor...ory&path=37_80
Or even this:
http://www.scopestuff.com/ss_foc1.htm
If confined to the rear-mount focuser, I see nothing wrong with your original choice.