Mike,

I think stacking the blocks in that slot may be strong enough for headsails. I thought having a 3/8" bolt through the center of the sheaves would handle the loaded stress of the main halyard better long term. My rationale was, we are getting away from the cast aluminum fittings, why not 'two birds-one stone'.

Do you think the mast would have to be reinforced around the slot? If so, how would you proceed? You know-What Would Mike Do?