Simple weapon model modification

Greetings! I didn’t believe that this day would come, but I finally found a SWEP for Garry’s Mod that perfectly fits my strict taste. I’m talking about H&K MP5 Surefire (light module) 9mm SMG. So there’s an MP5 included on Firearms Source 2, but the thing is that specific module bodygroup is hidden and there’s no way to display it in-game. I found this option since I was bored and decompiled some models, MP5 one between them and saw ‘ref_handguard_light.SMD’.
I went and tried to compile the weapon with this lovely bodygroup without luck, maybe because I am not that expert at compiling, whatever. I reached to rotate the weapon correctly with ‘snap rotate -90’ command on .QC and hardly dealed with some problem which made the arms like fly away (with ‘do not fix rotation on animations’ option when decompiling); but for some strange reason now the hands do not handle the weapon correctly. Here I leave a few images of what I am talking about:

I’m also attaching a folder with the decompiled and prepared weapon files you’d need to work on :

Anyone willing to help me out, please? I’m really dying to put my hands on this beauty and do some CQB training with it. I don’t think it can be very hard to satisfy this request, it’s probably just a little detail which is escaping from my mind.

If you’re trying to get help with a model, and not programming; then you need to bring this here: You shouldn’t make duplicate threads either.

How can you expect help when all you do is insult people?