Has anyone tried running the mainsheet forward along the tramp to a mid-point or further forward turning block/flopper with cleat? This would not change any loading/bending on the boom as force is still from the usual place, but sheeting angle to the crew would now be square to the hull. And there is no line coming down vertically to the tramp from mid-boom point, creating interference issues during tacks/gybes.
Tramp tensions might play a part in sheeting performmance...perhaps running non-stretch vectran/spectra under the tramp to the corner beams and/or gunnwales to take loads might cure it?

Mike.