Are you sure that you intepretate his writings correctly ? I'm familiar with his concept although via other sources than Gentry himself. These sources all express that adding the jib hurts pointing LESS than what would be expected from superpositioning the two single sails to form a double sail rig. In effect the maximum drive of the combination of the two sails is found at a smaller pointing angle than would be expected from just adding the characteristics of each sail individually. The explanation for this is than given via upwash and downwash principles. This is somewhat different from your interpretation.

Wouter