No Damage
Dan, seems to me that cowling would add more than a couple of mph, remember drag going up as the square of the speed, but you people are the ones flying them, not me.
But I am firmly of the opinion that smaller diameter and higher pitch props would give you a healthy boost in speed, always with the proviso that the plane can pass successfully through the highly inefficient low speed regime getting to the speeds you want.
With a real high pitch, the takeoff's a b****
Bill