Apart from the Peterson Engineering upgrade for the LX90 focuser itself - this is the ONLY thing you need to add to your LX90 to give ultra-precise focusing (well, maybe I need to add a $0.10 Hartmann mask made from a discarded cereal box !!)
And even this 'mod' can be upgraded - providing you can afford to purchase a toothpick (preferably un-used, and un-chewed - we are supposed to be scientists after all). Stick one end in anywhere on the circumference, and you have instantly created a 5:1 reduction 'gearbox' for your focuser. And all with NO image shift.
Yes, I really mean that - I have absolutely no detectable image shift whatsoever when I focus - even at f/20 with a Barlow. I use a second toothpick (yep, no expense spared) to act against the first when I want that final critical adjustment.
Motorised gizmo-justers - who needs them?