KSYN Pilot, a little more information would help inform the discussion:
-What is your field elevation? Typical density altitude in your busy season?
-What is your fleet mix? Heavy two-seaters with big pilots? Light single seaters? Water ballast?
-How is your 160hp PA-18 configured? Especially what propeller? Exhaust system? Engine time and maintenance history? What is the empty weight? Other modifications?
-What is your budget like?
-What are your mechanical maintenance and repair resources?
That said, there are many glider operators running 180hp Supercubs, especially in high density altitude situations. The original 0-360 STC's came out of Dave Johnson's operations at the former Black Forest Gliderport, ~7200' MSL and his towing contract at the Airforce Academy, ~7,000 MSL in the mid-1960's. The Academy has cycled through a few contractors since; the current one is running Cubcrafters 180's, specifically configured for towing (rumored to be heavy), and the previous one had light 180 hp Piper PA-18's. A significant part of their towing involves fairly heavy DG 1000's.
Thanks. cubscout