Hey Snoop.....
that sounds like it is indeed hauling some serious mail !!
Nice find on that 14x12 - seems well matched for the altitude too. And 9600 rpm on the ground is perfect for a speed application. I would imagine it is unloading up into the 10,500 range in the air and really singing.
Sure seems like a good ARF value, and a good powerplant combination too. Best of luck with it.
Bob