Most folks who install the LEM on an HK45 or HK45c pistol use the parts that eliminate the safety lever from the pistol. It is a simple thing to use the safety lever instead of the LEM axle while installing the LEM kit and retain the safety. A few folks have opted to do that. It will have no decocker function--only safety. The biggest question for USN06 is whether the LEM axle came with the pistol when you bought it second-hand? If not, you'll need to purchase one from HK or from one of the several parts vendors.