I am chaging the sights on my RIA GI 1911 with these http://www.fusionfirearms.com/servlet/the-678/Sight-SET-,-White/Detail Punched out the old rear sight and the new FF sight basically slides right in! problem is there is a sizable gap between the frame and underside of the sight. 4 pieces of printer paper fit easily in the gap. What do I need to do to bring the sight down? I assume filling the bottom of the sight dovetail would not help as then it would be loose in the dovetail right? Thanks.