I have a Z-6 w/115 opti, I was not happy the 1st season I used it due to vibration while idling, poor hole shot and boat would lean to drivers side. All this has been fixed, I'm now very happy. Got factory rep. involved and BPS finally test drove the boat to see 1st hand. They fixed it by moving battery to other side and trying many different props until they got it right. Since I run at 5,000 ft. my final prop wouldn't work for you. Suggest you do what I did and have your dealer take boat to local lake with lots of props. The 21p prop is really set up for top end, I was more interested in a good whole shot with 2 people and full livewell. I'm now very happy with boat, and my lake has a 35 mph speed limit anyway. The boat runs a 45 with no prob. with the 16p smaller prop.
I hope this helps, this boat can be fixed.
tom