Vic - here is the class rule for reference. I added the emphasis on the applicable area. This will help you get the rig in the correct position so everything supports OD sails and tuning.

5.7.3 Position of the mast shall be fixed at the deck 3505 mm plus or minus 13 mm from stemhead tip to the front edge of the mast. And it shall be permanently fixed to an immovable mast step so that the forward edge of the mast is not less than 25 mm aft of the forward vertical face of the molded step in the sole liner.