Last year I installed a new control on my trim tabs that does just that. The way that it works is like this. You set you boat up for the desired cruise speed and attitude desired. Hold in two buttons until you get a steady light. Now whenever you set your throttle to that desired cruise speed, just hit the power button and the auto feature does the rest. .IF two people got up and moved to one side of the boat, the auto tabs would keep the boat level. It is a pretty cool feature and not very expensive to install.
https://www.westmarine.com/buy/benne...FYaPswod7_kA0w