Hi Eric,
As you know I have nothing to do with the level of any boats' PN. When a boat starts out new, the initial PN is a guess. The ARC17 PN was based on the SC17 and adjusted for square top main and spinnaker and boat width. At Tradewinds Rick did the calculations. He used a spinnaker adjustment factor of 0.972. I think US Sailing uses 0.96 but, he is the boss at Tradewinds. Anyway, race data will bring it in where it belongs quickly. Tom just needs to sell a few and get them out there racing.
Good Sailing,
Bill