You asked for updates on the kits performance. It has now been a few months and a few more tins and she is still tight as the day she was installed. I put the brass screw cup kits on my R1 and R9 yesterday. All but My R7 now have them. Of course the R7 already has a metal insert from the factory. I now have the kits in a 350, R1, R9 and HW97. I will only update further if there is a problem. Folks if you are tired of having to tighten your stock screws contact:
http://www.mac1airgun.com/ and order the screw cup kits. It really is a nice product.
James