For clarification: For class normally without spinnaker carrying a second one or carrying another headsail in a long distance race, apply both modification factors.
For class normally with spinnaker carrying one or more additional headsails, apply modification factor for each.

(the above taken from the Portsmouth Multihull Modifications table at USSailing.org and it would seem correct to apply mod factors for each additional sail carried.)

Hope to see you at Turnback
sail fast