What is your max RPM with your average load? What is your motor's max RPM range (per manufacturer's specs). If you are already hitting the top of your manufacturer's max RPM range now with an average load, then you may have a bit of room to play with a higher pitch prop (each 1" of pitch you go up will steal about 200+- RPM). If you aren't hitting at least the midrange of manufacturer's max RPMs then don't even think about going up in pitch - you'll just shorten the life of your motor. As to motor height, since you have a jack plate you should be able to move it up and down to get the best combination of speed and control before you start ventilating. One more thing - be sure you don't run it so high that your water pickup is starving for water. There are low-water pickup kits available for some motors might be available if you ever do really need to get it that high (although getting it that high is normally less about speed than it is about being able to run shallow).