Outboard questions on 14' Fiberform runabout

My 14" Fiberform runabout seems to plane out easily with two people aboard but has a tendency to cavitate the prop even while running a straight line. The speed of the boat seems low for the rpms of he motor. I am running a 50hp merc four cylinder with a new 11" pitch prop. The boat has a hard chine and fairly deep V style hull and is rated for a 70hp motor. Am I running to little hp for this boat or do I have options with adjustment of the motor height and adding a cavitation foil to my motor and will this aleviate any of my problems? Any help and suggestions are greatly appreciated and welcomed

 

In addition I am getting an odd spray pattern on to the transom. Adjusting the pitch of the motor away from the transom does affect the spray pattern but perfomance of the boat gets worse as well.