By moving the boards forward and thereby changing the C of LR you tend to induce more weather helm and it will appear that the boat wants to point up higher. Move the boards back and the reverse occurs (i.e. lee helm). The ability of the boat to actually “sail” higher with the boards forward, (if that is what appears to happen), is primarily an illusion just because the helm always wants to take the boat higher doesn’t mean that it can actually sail higher (with advantage). The best set up is when everything is balanced I.E. the C of E of the sails, together with the C of LR of the hull/boards, and the “tune” of the rudders.