To anyone who is experienced..
I tried an !8 x 14.5 four blade and Im getting some ventilation. I do not want to Lower my motor because I am experimenting and my 19 trophy works pretty good but Im not into my Rpm range yet...(hence the 18)

My question can the 18 be trimmed to (14 or 13.75) and cupped? or is that just to much?

The Prop is a power tech the boat is a 20 foot ranger and Im at 5 to 6k altitude.