cknight98,
I have two of the P-11s and two P-32s. I have a 13 rd mdl 59 S&W mag that I sometimes carry for the P-11. I don't have the sleeve for the bottom of the mag, but it works quite well without it. I carry it with the 10 rd in place and the 13rd as a spare. The S&W mags work great without any modifications at all.
Stay Safe,
Savage
