M_Boats: reefing on M17 boom

Hello All, I'm building a new boom for a M17 and I need a little help on installing reef eyes and blocks on the boom. My sail is a reasonable new Elliot Patterson (sp?) with 2 lines of reef points. How far aft of the grommets on the leach should the anchor points on the boom be? I assume they should be aft at least an inch to hold tension on the foot of the reefed sail. Thanks, Ches Sugg