I’ve put an Ultimak on a Zastava M85 in 5.56. I left the stock wood lower hand guard on it.
No issues. But I also haven’t done consecutive mag dumps to torture test it.
I have my RDS co-witnessed but honestly, when you put one of the smaller RDS setups that far out in front of you, the sight picture through the sight gets awful small. You see the sight picture, the sight housing and every other thing out there in front of you all at the same time. It’s still faster than lining up the irons, but it’s noticeably less clean, for lack of a better word, than having a RDS closer to your eye.