... The only time it was really bad was when the set screw was perfectly parallel to the split middle seam. I tightened it too much and crushed the two halves together. But if I'm careful, I can avoid that.
...
You know the little tab that you break off to sit the pot flush in the enclosure?
That’s the one…
It’s a snap…
Where’d it go?
Bam! Right up the snout of the ol' Spice Weasel!
It just so happens that, in most cases, the little breakaway tab is the perfect size to jam into the split, thus preventing a knob’s set screw from pushing the split together and wrecking the pot right away or through long-term fatigue.
I've jammed it in and it's usually solid without any additional fuss, BUT...
If you're unsure that the little tab won't stay put or you find a pot with a tab that most definitely shifts around in the split (like the one in the above photos), then just add a dab of solder to keep it in place. This one will require a dab of solder, on either/both side(s), not on top, so the severed tab sits flush with the top of the split, allowing the knob to sit all the way down.
Of course, only do this tab-trick for set-screw knobs, the knobs meant for splined split-shafts don't work so well once you solder the tab in.
I rarely use split-shaft pots, and prefer set screw knobs...