Addon help

[Vex]

So as a fan of MAJ. Drumheller's YouTube channel (Jester418), I've noticed that he tends to use the CompM4 with a x3 Magnifier on RHS weapons. I've tried again and again to figure out how he managed this but couldn't figure it out, so i'm here. If someone could help me out as to how to get MRT and FHQ accessories to work on RHS weapons I'd be much obliged.

Thank you
- Vex

[Kazanski]

Joint Rails

http://www.armaholic.com/page.php?id=23242

[Vex]

I had Join rails installed so I reinstalled, nothing changed. Still not able to put other sights on.