If you can't find it rating for the wing, then
send your app in with the rating for the fin keel. If they don't like it the race comm. will change it to what is correct, or ask you to submit an application for a one-off PHRF rating to their PHRF committee. If you happened to find a rating for a wing keel for another geographical area, that rating wouldn't necessarily be accepted in your area anyway, as local PHRF committees can revise ratings based on the prevailing conditions in your area.Given that it's a charity regatta, the race comm. want as many participants as possible, so they'll be accomodating.