Oh yeah, I remember your boat. Nice.
I would retain the sub-surface drive set-up, it functions very well. Upgrading to a CMB .45RS should provide additional speed increase, able to run more prop.
Just to give you a guide:
My Rossi R65 powered Spartan Streaker sub-surface drive is set at 3/4in drop parallel, with very slight angle adjustments to control ride attitude. Using X450 and X452 prop.
My OPS 45 powered Youngblood 38in mono has sub-surface drive set at 5/8in parallel, with very slight angle adjustments to control ride attitude. Using X447 prop.
Both these mono's are somewhat similiar in hull surface layout.
My Streaker exhibited very fast straight-away speed, to the point, that it would "fly" off the water a few times. As I mentioned I would correct this by adjusting strut angle accordingly (prop-end down- I forget if positive or negative?). I really believe that this tendency to fly was partly due to the almost 1/4in-wide flange, where the deck and hull join, functioning as a "wing". Just my take