I have a Red Dot with a QD lever and it returns to zero every time on my S2K. Not an issue. (Holosun 515C)If price were not an issue, CX4 Storm for me. Decent sight picture, much easier to rack charging handle, has a bolt release and last shot hold open
The only thing the Sub 2k has over the Storm is it's a bit lighter, and the ability to fold. But if you mount a red dot on it, you lose the ability to fold it (unless you use an offset mount)
I wouldn’t recommend the Sub 2K. I have had 2 and neither one of them were reliable. Also terrible ergonomics to the point that they are unpleasant to shoot.