Just learned the Plattsburgh Rod and Gun Club has club level IDPA every Wednesday evening, and decided to give it a try. The club member I spoke with said some modifications are OK. I'll be shooting my G27 with my black, blind marked LWD 9mm conversion barrel. For magazines, I have 1 single stack 10 round 9mm mag, and a G26 10 round magazine, plus the three G27 mags that came with my gun. I have found that the gun runs fine when I load the G27 mags up with 9mm and shoot. Does anybody think I'll get a hassle about using the .40 caliber magazines with 9mm? It would sure be easier to have 5 mags pre-loaded, or shouldn't I need that many?