Keep gudgeons well separated to keep upper gudgeon lightly loaded. For swim step transom, use stern pulpit to support top gudgeon. This is a mat-cloth combination totaling 25.3 oz. Selvege tape lapped around leading and trailing edges. Only one bolt in rudder and one bolt in transom, fitted loosely.
Additional bolts added after top gudgeon is in place to establish alignment.
This determines the maximum force on the rudder blade. Assume the force is centered between the lower gudgeon and the blade tip. Use 10,000 psi as design stress in low-tech laminate. Or use allowable shear stress of 6,000 psi for same result.