I am joining the dark side. A bone stock NSR50 is too long in the tooth to keep up with the 4s MiniGP bikes. Our spec class puts the NSR with the Honda NSF100 and Kayo GP 125.
My donor bikes are: 2004 Honda NSR50, 2002 Honda XR100
It went really well. It was a nice change to be running in the top three instead of the back three. The kayos have extra pull, but overall it was well worth the effort. All in all very happy.