bat443 wrote: In commercial operations these would be required
on both an hour and calender basis, which ever came first
Howerver in glider tow operations, the towplane operates under Part 91, rather than the more rigid Part 135 maintenance requirements. But on a tug, it's either max climb on tow, or descending, no performance advantage to a CS prop, and the maintenance is a lot more.
The last large glider tow operation running Scouts was the Fisher Agency, contractor to the US Air Force Academy. They ran the 1A-200-HFA-80/39; factory "stock" pitch was 80/41. Bear in mind this was at 7000 MSL, with high density altitudes much of the year. I ran the same 80/39 for many years at 5500 MSL with good results.
Thanks. cubscout