Another solution is to just use G17 mags for the reloads. Once you’ve gone to a full Batman belt, there’s really not much reason *not* to just use entirely G17 mags on the range.
Only 15-round Glock mag I use at all now is the one in the gun when carrying just to make it easier to conceal. My reloads are almost always all G17 mags for both my G19 and G26, and the G19s all have 17-rounders in them when stored for home use.
It just occurred to me that I ought to add some +2s to some of those G17 mags…
Question for the OP (not criticizing, genuinely curious) why a double ouch and not two singles?