I remember getting a aerotow retrieve behind a supermonk in a K18, climbed up to 5000` for the cruise and as we levelled off he must of forgot i was a wooden ship as the speed rapidly rose to over 100kts, he said later he slowed down when the wing tips stated to droop! (with the washout if you`ve ever seen the k18 going fast, VNE was 108kts!)
Sometimes you can have to much power, on the other hand i towed a nimbus 4 with the Auster and had to go flapless to give him enough speed to get airbourne, not good when the tug is climbing and the glider is still firmly on the ground!. I could see him almost waffling behind in the mirror. it was a very slow climb with a rather warm engine. I`m sure he appreciated the little black spots over his aeroplane from the drippsy major!