If I've got this right, USPSA Multigun matches can use traditional hit factor scoring (major/minor affects target scoring) or time plus. 3GN and the other 4 gun matches I've shot were always time plus scoring. So major/minor do not come into play.
Even shooting minor with no floor, you still need to be able to knock down steel. I try to stay above 130 PF and have not had problems.
The slide mounted red dot opens up your selection of holsters, For 3 gun, retention and protection of your handgun requires more than most of the Open rigs found in USPSA. I'm not saying it can't be done, but I really trusted my CR Speed holster until I saw a competitor at a major match outrun his handgun.
