I think, repeat think, you're probably fine. The reality is that if the airplane is accelerating, then there is an inbalance of forces. At some point, drag will grow (square of speed) to the point where it balances thrust and the airplane accelerates no more. Certainly at terminal velocity there will be some level of pull (friction drag) on the canopy in excess of what it experiences at full throttle on the ground. However, since that prop likely puts out a fair amount of blast, if it appears to be holding well, then you're probably ok.