Sorry Yanky, I didn't mean to be so criptic. I shoot IPSC (USPSA) and IDPA, and use essentially the same gear for both. In USPSA Limited 10 Division, you are allowed to shoot an iron-sighted, non-compensated 1911, with no more than 10 rounds in the mags (single stacks and wide-body guns compete togther, as nobody can load more than 10). Holsters, belts, and mag pouches are just like Limited and Open divisions; what I somewhat-derisively call "robocop" gear. Plastic or metal "holsters" upon which the pistol is often precariously balanced, and with no practical application.
IDPA Custom Defensive Pistol division allows similar guns (nothing that adds much size or weight are the real limitations), loaded to a max of 8+1 rounds. The gear must be practical holsters, belts, etc., like you'd wear on the street.
Custom pistolsmith Richard Heinie started what he calls the "1911 Society", which sponsors an annual match called the "Single Stack Classic". Since it's Heinie's match, he can do what he wants. It is essentially an IPSC/USPSA match (scoring, rules), shot with IDPA gear.
When USPSA instituted Limited 10 division, they also added Production and Revolver divisions. The latter were limited to IDPA-style (practical) gear, while L10 was allowed the space-gun rigs that predominate in Open and Limited. I would like to see USPSA align L10 with Production and Revolver (since they shoot together at Nationals), requiring the practical holster, etc., which would make L10 essentially the same as Single Stack Classic.