I just picked one up(SU-16A) last Tuesday night. I have not fired it yet, but I will post a report as soon as I do, should be Sunday.
As far as all else goes, first, for a poly, collapsible rifle its very ridged and well built, there is no flex in the stock what so ever when deployed, even the "bi-pod" forend that looks like it would be "squishy", is not at all when closed. The SU also fits me well, I love the way it shoulders.
I have an EOTech 512 on for optics, the front sight of my A does come into the view looking through the 512, I won't know how this effects shooting until I get to fire the gun. I'm not planning any accessories out side of what I have (EOTech sight and two 20r PMAGS) If the front sight becomes an issue I might consider removing it and adding some kind of comp.