John
Good luck with this venture. As we discussed via PM, I would gladly give you my mag extensions if I still had them.
The two mag extensions I received were well made but were disproportionate to the R9, looked awful and did not enhance performance of the gun. I hope this is not your experience if you get the mag extensions machined.
One thing for sure: you are looking for the definitive rig. You have your Robar R9, Rafter S holster is in the pipeline..... When do you quit? Or, what's next?