I took a look at the 17mm Bourns and Alpha pots with push-pull switches. I have to say they certainly don’t look very different. Aside from the slightly larger diameter of the shaft it’s hard to tell what’s different. Has anyone compared with an Ohm meter?

I haven't got much experience with the 17mm pots, but I have pulled apart a lot of 24mm pots (long story), and I always check them with an ohm meter before putting any pot in any project. I can tell you that 24mm Alpha, Bourns, CTS and CME pots have similar tapers, and are of very similar manufacturing quality. Bourns, CTS and Alpha are very similar when you take them apart. CTS is different, but it is more the way the resistor wafer and wiper are mounted--which is why they are stiffer to turn. The manufacturing quality is about the same in all of them.

It seems totally possible that the Alphas are less consistent in their quality control than Bourns. On the other hand you can get four Alphas for the price of two Bourns. As long as you check them on a meter against a pot you know is good before putting them in the guitar isn't it about a half dozen of one six of the other?

At the risk of saying something heretical, enlarging the holes seems like a lot of trouble to go to when there are pots available that look to be of nearly identical manufacturing quality. That said, if no one has done it, I'll sacrifice a couple to see if I can see a difference in the guts or on the meter.