I recently purchased a XD9 subbie for my wife, the owner included a NIB set of AmeriGlo night sights. My problem is upon installing then the front sight slides in and falls out. I assumed that the front sight is held in place by a pressure fit. Is this correct or must the new front sight be staked to stay in place. The sight are for the XD according to the packaging. Does anyone have any experience with these sights? Should I ebay them and get some other brand?