Actually I don't know if I'd want to glue mine in place. Being able to remove it on occasion is a plus for me. And sometimes I think the sweet spot can actually move, based on seasonal changes, string tension, bridge height adjustments, and other variables I'm probably not even aware of.
But I do trace the outline of the bridge wing's "foot" on the pickup itself so I can reposition it easily. I even use different colors for multiple sweet spots. It probably helps that my pickup has a wood casing (Rev Solo) - it would be harder to trace w/ a pencil on a metal or rubber-cased pickup I suppose.
On another note - These pickups can be super sensitive to how snug the fit is. But if you want to try shimming the p/u with like a sax or clarinet reed, a business card, or even wrap(s) of scotch tape, it might make it harder to get bumped out of position - but would also affect the tone probably.
