Bob Carlton once towed his Salto (before he put the jet engine on it) behind Dr. Ray Vetsch's "Turbo Shark," running a Walter M601T 780 HP turbine. Climb to 6,500 AGL release altitude was about 65 seconds and they were running at the Salto's redline speed (155 knots). After twanging the release, Bob gained another 800 feet.

http://turbo-shark.com/Plane.aspx