I had great experience with Chuck from Kelly Enterprise. He answers the phone night or day and will give you his input if you ask for it. I also had great experience working with Blaine from Atlantic. They both appear to be class outfits IMO.
I bought a VKE-91K from Kelly and sent off the collapsing stock to Bill Springfield for a new buffer. It was not shootable with the standard buffer...bruising doesn't begin to explain the colors one will see. I also bought a heavy buffer from RobertRTG HK Heavy Buffer by Parabellum Combat Systems, HK Recoil Reducing Heavy Buffer for HK91 G3 PTR91 HK93, RTG Gun Parts for my A2. Sadly I have not tried either stock out since getting the new buffers.