I’ve never been a believer that you get optimum trim pin setting by visually putting the cavitation plate parallel to the bottom of the boat. You have to try different settings because how the boat is loaded also plays a role here. You usually want the plate up some to lift more of the boat out of the water to reduce drag. Pushing parallel can keep too much of the boat in the water when up on plane.

Another trick I use all the time is once you have the trim pin set right; is to shim the motor up on the transom by adding paint stir-sticks under the transom clamps. keep adding and trying until the prop loses grip of the water when running in medium choppy waves, then take one stir stick out. You will likely gain one to three MPH at WOT, and gain some gas mileage (especially at the 3/4 cruise setting). Reason is you are not dragging as much of the lower unit through the water. Again – visually setting cavitation plate height doing this generally doesn’t work.
Dave