Interesting feedback, indeed I tend to find the Super Decathlon doesn't really seem to climb any better than the Super Cub despite quite a bit more power and a CS prop, I would suggest due to the wing configuration.
Thinking back in the mists of time when I used to fly for a VGS out of RAF Kinloss the local gliding club used to operate a Supermunk (Chipmunk modified with an 0-360 to give 180hp)
Don't know how easy they are to find for sale but assuming the conversion did not remove the aerobatic category from the aircraft I wonder if one of those might tick your boxes?
Details from Wiki:
"Supermunk Designed and produced by officers of the British Gliding Association (BGA),Supermunk aircraft were converted from Chipmunks by fitting 180hp Avco Lycoming O-360-A4A engines for use as glider tugs.[19] Operated mainly by the Royal Air Force Gliding & Soaring Association (RAFGSA), the Supermunks are still in service and used at major gliding competitions in the United Kingdom. It is also used by the Portuguese Air Force Academy as basic training aircraft and as glider tug."
Regards
UA