[tsubaki]

You can do it easier by using the skeg of the motor (with a board under it)
and the trailer tongue jack.
With the engine tilted down, place the board under the skeg and then crank the tongue jack till the skeg contacts the board.
Loosen the bottom engine mounting bolts then remove the upper bolts.
Crank the tongue jack up till the desired hole is reached. Reseal and rebolt the engine.
I'd level the cavitation plate with the bottom of the boat. Then measure to find out how much or many holes to be about 3/4" above the bottom of the boat with the cavitation plate.
That should give you a good starting point.

Keep in mind, on most boats the cavitation plate being level with the bottom of the boat is the normal starting point to see where the best location is. These V's have a pretty steep angle and may need to be a little higher than others.
There are other factors that will contradict this method but it's a starting point.