Just trying to help here. You have the sight mounted backwards, that's why it dosen't lay flat on the rail.
From PRI's Sight:
Rail Mounted Flip Up Front Sight
The new PRi forearm rail mounted front sight is designed just like the original barrel mounted flip up front sight. The rail mounted sight works on any rail that is mounted at the same levels as the recievers rail. The sight is designed to lay forward in the down position. The sight then can be raised and locked in the up position for iron sight use.
Will be in touch next week to get one.