I am a MItsubishi Dealer here in the Virgin Islands and install a lot of Mini Splits. I am wondering about how you feel about pressurizing the line set before commissioning with compressed dive air. We pressure test all line sets overnight with dry air at 600 psi and if they pass we then do a triple evacuation with Nitrogen and charge. For years we couldn't get nitrogen so compressed dry air was all we had other than loading it up with R-22. This has assured me of a callback rate for leaks at less than .01%