Depending on how masochistic you are, you can shoot a single stack .45 in Single Stack, Limited 10, Limited, or Open. If you already have a belt-full of 8-round mags, then go for Single Stack. If you want to race a little faster, get a half-dozen 10-round mags, and shoot L10. I've been shooting L10 almost since the day it was introduced, and it is a lot of fun. You are often faced with target "arrays" requiring eight rounds in USPSA, and having a couple of additional rounds gives you flexibility in target engagement and reload strategies. Shooting Single Stack, you have to do a lot of stop/start and standing around to get the round counts and reloads coordinated, and while it's the same for everyone, it's hard to "race" when you're standing still.