I find that with the 15 round mag inserted, the gun fits my hand slightly better than the 13 round mag with the +2 MagGuts kit.
Then again, I usually find myself carrying with the 10 round mag in the gun, and carrying a 15 round mag as a spare mag.
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I like the MagGuts +3 kit on my 10 round, gives a little pinky rest without being larger to conceal. I'm on waiting list for +2 for my 13 round mag--will be my extra in the pocket.