My Lazer 45 runs great with the shaft centerline about 5/8 " above the bottom of the boat. Make sure the shaft is parallel with the bottom of the boat. Trim tabs need to be 1/32" above the bottom of the boat.........start off in a neutral position. Center of Gravity needs to be around 30% - 32%. Adjust the CG before you start bending the tabs DOWN to get the nose down ( if that's what you need to do ).
My boat with a stock Zenoah runs around 50MPH.......52MPH on a good day. Hope this helps.
Dick Tyndall