I've only ever had fixed sights on the Glocks I've used for production and the .40's I reload for USPSA are nowhere near factory. I do know that I need to cover an 8" plate 2/3 of the way up at 20 yards. This is a different sight picture than I need for the Limited gun which is almost a 6 o'clock hold. Then again, I don't shoot production very much. If you can't adjust for the fixed sight, then adjust the fixed sight ... send the slide out or get a local smith to put a bomar on it for you.