I installed a longshot full length, 15.4 inch piticanny rail to the top of my highpoint 4095. I mounted a set of magpul mbus gen 2 sights on the rail. I have the sight pin adjusted all the way down to raise the impact point and it is still impacting 4 inchs low at 20 feet, any thoughts on remedying situation? I'm thinking of adding a .5 inch utg low riser to the rear mbus, not sure if I am looking at the sight geometry correctly, considered filing the front pin to achieve aim. Trying to avoid trip to the gunsmith, if I am missing something simple.