J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Harken Roller Furling Assistance

I am going to switch over to a Harken III, unit 1 roller furler. Because of the delay in installation I need to get a revised "I" dimension for the sailmaker to cut the new headsail before I can actually measure the distance with the new gear installed on the boat. Basically I am looking for the length from the head to the tack on the headsail cut for this type of furler. Does anyone with this set up have this exact dimension?

Thanks!