bugger - so many good questions there and almost no answers...
read
this article - and can not - will not - must not - move the primary. Cutting the tube? Never!
But it mentions the other gear to achieve something similar:
low profile focuser and Coma corrector.
Intriguing: the focus point is
closer to the secondary - contrary to my afternoon experiment.
Arif, you solved it with springs and long screws? Did you follow any internet article when doing it?
magical optics ...