Is the engine a long shaft?
Have you a standard length leach mainsail ?
( A standard length leach mainsail will have the boom looking parallel to the sheer of the boat when looking from the side of the boat)
Is the mast set at the correct rake, 23ft 6in from head to transom. See Class Tuning guide for more information.
Transom brackets will do a better job with them being lower, all the backing plates and stiffeners can be got at inside the back tank!