Jesse, try riding high thumb (put your strong hand thumb in on the little shelf that's on the upper rear of the grip, the your weak hand thumb points forward right under that).
Also, some competition folks (especially women) buy left handed SVI and STI frames so that they can use their middle finger to eject a spent mag. Once you get used to it, it's very quick. But it WILL release mags if it's an extended mag release (however, extended mag releases aren't a very sound idea in combat, if you ask me).
