M_Boats: M15 and M17 Spinnaker handicap

Does anyone know if there is an established Portsmouth Yardstick handicap for the M15 (and/or 17) flying a spinnaker? In the Delta Dinghy Ditch race this weekend, there should be a few M boats including mine, and the race coordinator pointed out that in the past they had been (incorrectly) using the same non-spinnaker rating for M boat with and without spinnakers. He said if our community has a standard we agree on we could use that, otherwise we'll probably have to race in the 'cruiser class' which is handicap free. Sincerely, Tyler Backman '81 M15 #157