Good info Dennis.
My FP 10 started life as an FP-S with the rear needle. I replaced the RN setup because I could not get it to seal. No matter what I did, there were air bubbles in the fuel line. After fiddling for a while, I simply replaced the RN setup with the correct needle through the venturi.
I measured the venturi that came with it—6.0mm ID. The Tower web site says 6.0mm ID for the FP 15 venturi. If that's correct, you are almost certainly good to go.
I was a bit surprised but as I said above, the spraybar is 4mm OD—necked down across the venturi. I think the NVA may have originated in the 10 FSR.
Based on your info and some desk research, it seems that your conversion should be good.