Not a fan of a 180hp towplane with CS prop--a fixed pitch (climb pitch) is lighter, simpler, cheaper. *I've towed with a 172 with 180hp--it was a poor towplane. *Currently use a 150 with 180hp and climb prop--I've towed max gross
Duo Discus adaquately with it at 3000 foot density altitude.

Fixed pitch is alway lighter and cheaper, but it would impact the
usability/resale of the aircraft. a C-170B is a much different
towplane than a C-172 because of the gear, yet it can be used for more
things than just towing... not so much for the Pawnee, where a CS prop
adds only a knot at cruise...

aerodyne