Need ideas to stop porpoising?

[Bushwacker]

I'd go 1" at a time and try it out. With engine trimmed as high as possible without porpoising, you should be able to make a moderate turn at cruise speed without ventilation/cavitation, although you may have to trim it down a little for hard turns. It will also help if your prop has a fair amount of cup in it as this seems to allow you to run a higher mounting position. Years ago I switched from an aluminum to an OMC SST stainless prop, and raised engine 1" as they recommended. (Engine was originally mounted same as yours with cav plate lined up with bottom of hull.) I picked up about 3 mph in top end, as was advertised. You may find that you have to run with engine trimmed a down a little more in rough seas to prevent ventilation or cavitation.