I don't know to much about inflatables. I have used a small outboard alot on small John boat and Vbottoms. The best result I have ever had was to put more weight in the back and to get it a little deeper, but you may just have to go to a longer shafted motor.

Once you go cat you never go back! Nacra 5.2 (Elsies)#1499, running an inter17 spin!