So I got my first HK. It's a fullsize USP 9. However, the insert in the front sight is missing and I need to replace it. I've done some searching online and I know I need a 6.8mm sight. But I can't find one. I have found a 7.0mm sight but I'm not sure how that will affect the POI. Will these work? Anyone know where I can get a 6.8mm front sight? Thanks in advance!