looks amazing! any trouble when installing the ras? thinking to get one of that for mine too. Thanks!

It's been many years since I installed it so the install is a little fuzzy in my mind. It's not a real Knights rail, it's a replica. The real ones were nonexistent when I got it. I don't remember who made the rail but it's pretty well made. You would need an adapter to extend the front of the GSG receiver since the GSG receiver is shorter than a typical MP5. I remember I had to do some milling into the adapter I got to make it fit correctly. I also had to lower the rear of the rail area where it clamps to the adapter so the rail would sit level.
It wasn't necessarily the easiest thing to install. It's remained rock solid for many years and thousands of rounds though.

11 years later, I am still making a project out of my GSG. RIS II rail will finish off a little upgrade. She's got less than 1500 rounds through her.
20201018_232340 by Vito Corleone, on Flickr" />

Popcop, your post caught my eye. Where did you locate the pistol brace and
Was there any modification needed to make it fit?  
I made a few changes to mine also including replacing the stock barrel with a threaded one.

Here is my little project...

GSG-16 with GSG-522 conversion kit.
Dlask Arms 9" barrel conversion
Magpul front grip
CSM VFG
Top rail delete 3D printed
HK MP5 push pins
HK MP5 rear sight
ICS lower conversion
B&T Ambidextrous Sling Pin
B&T MP5 folding stock
Romeo4T red dot

@shurick

Oh my goodness!! I need more details on this gun! Especially the barrel and stock. I have a GSG -522 SD lightweight that I have been debating going longer and making a .22 G3 clone as I already have the handguard or SBR it and get a new barrel.

Is the stock an airsoft version or the real deal? How is the Magpul handguard fitment? Any modifications needed?

I wish I just got the pistol version back in the day. It would have been so much easier. But the whole braced pistol thing wasn't around then really.