Yes, you are limited to 10 rounds.
I have two choices:
1) buy 10 rd mags and use them for both IDPA and carry
2) buy SA 17rd mags and use them for both IDPA and carry
If the gun will not fit in the IDPA box with a SA 17rd mag in it, then option 2 is out.
Either way I go, I'll eventually end up with some of both styles of mags. Right now, I have limited funds to spend.