According to Vosper drawings the KD Perkasa shaft angle is 10 degrees. As Deadbeat stated the trick is to get it as shallow as possible, one thing to add is to leave a little extra space between the hull for a slightly larger diameter propeller than the one you have as you may want to do prop changes later. Also, fit a rigid tube over the flex coupling as that will help determine the motor mount position and keep everything dead straight whilst doing the job.