Drop-leg holsters, they're cool arn't they? Well, as the head guy at the (now sadly defunct) South Yorkshire Airsoft used to tell us 'they're great if you have arms like a gorilla'!
It's a valid point, as all the youngsters seem to love that low slung holster look but have absolutely no idea WHY it's low slung in the first place. No, it's NOT because cowboys wear their holsters like that - it's what's known as a 'sub-load' carrier, designed to be worn below a tac vest or body armour.
I have never liked these low-slung holsters and have always bought good old fashions belt holsters (with a close-able flap). I like my pistol high on my hip and as I prefer chest rigs rather than tac vests they are not in the way, but easy to get to.
Having said all that I came across a very good video today explaining all this and showing how best to fit a drop-leg holster...One of the most important points being FIT and keeping the rig STABLE...
I have seen countless numbers of young guys wearing drop-leg holsters at airsoft sites who's pistols flop about when they run, and even fall out, because they have not adjusted their holsters properly. One poor guy even lost his pistol (not having realised it had fallen out until the game was over).