The PSA Rock does look very promising and quite the value:

I'm looking forward to see what the reviews say about it.

I've got a bunch of the 20rd FsN mags, plus a FsN and a MAC that takes FsN mags, so sticking within that platform makes the MK3 more appealing for me. 

That said, I may end up picking up a 57 rock down the road; at about 1/3 the cost of the FsN its hard to resist. 

I think the rock with an acss Vulcan holosun will make one hell of a companion to my foxtrot Mike.

This is the nice thing about my universal holster on my war belt, I can jam just about anything in it lol.

I've actually been looking for a universal holster; which one are you using?

Warrior assault systems universal... I have two and I absolutely love them!

Here's a nice picture illustrating why I love them.

So as you can see here there's actually a physical locking mechanism that grabs the front of the trigger guard and it comes with a spare block in a Different shape for more squared off guards etc.

The important thing is my gun feels extremely secure and isn't going to come out even if I eat it and roll down a hill uncontrollably. 

The thumb break Is intuitive and manages to be very easy to release if the holster Is on you while being pretty difficult to actuate if you are reaching from it to try and take someone's gun.

They're also pretty reasonably priced. I got my multicam one from gear zone tactical, the coyote one is because eod-gear took my money after saying it was in stock on their site and after I hadn't heard anything from them for 3 weeks I contacted them and said hey what's the deal?

They literally told me oh yeah you can't actually expect us to know what we have in stock blah blah warrior assault systems THINKS They might have materials to make more in 6 weeks...

Had I not contacted them I would have just waited 12+ weeks before I maybe got one.

Moral to this story, unless you're doing agency ordering don't order from eod-gear.

P.s. warrior assault systems themselves had to intervene to even get them to send me a coyote one and refund me.

I know you didn't ask about this part but when you have an experience this bad it's important to let the community know.