while trimming; its very easy to damage those pots once they are soldered to PCB!
I'd secure the pots firmly... best is to mount them to the enclosure...
or make a small jig ( small aluminium that u can hand held, or vice ) , and use the pot's nuts to secure them, and hold from the jig, (make sure PCB is on flat bed too)
when u start cutting, u actually putting a lot of force on pots, u can damage PCB legs, or even break the
pot very easy!