Many years ago when taking the class required for the MI carry license the instructor (county sheriff) told one student with a horizontal shoulder holster "no effing way will you go on the line with that rig, you'll sweep every one behind you and for all I know you are a dumb mother f**ker". Wouldn't let him continue until he got a plain old hip holster from his car or someone else.If it was the eighties, maybe?
The reason we got away from those, is that they are impossible to be modern day safe. No way to not point the gun at yourself and who knows how many others? Every time you draw or holster.
No competitive shooting sport will let you on the line with that holster. I cannot imagine any firearm training class will let you on their line either, even the crazy ones
Ended up using an Uncle Mike's cheap floppy.
The guy and his girlfriend had a few other issues as well but got straightened out, at least for the class.