I've had good luck with OEM and Pierce +2 and +1 (pierce only) extensions in the 9mm doublestacks.
Mixed experience with the TTI +2s in my G43 mags - the ones I installed didn't work, but the complete mags I got from them did, so very possibly just my fuck up. Vickers +2 and Piece +1 43 extensions seem GTG but I haven't tested them nearly as much as the doublestack extensions.