ATC Watcher,
Good observations from Crankshaft and Unusual Attitude. I'll chip in with my view. I have lots of towing time in both flapped and un-flapped Citabrias and in Scouts, which are non-aerobatic, long-winged, 180 HP flapped Citabrias.
I've have flown Super Cubs on wheels and floats, but I have never towed with one. However, I have been towed by Super Cubs and in my experience, the 150 HP Super Cub performs on a par with the 180 HP Scout, presumably due to the lighter weight. Neither of them are as good as a Pawnee, with its extra power.
So I'm guessing that the Decathlon, with its smaller, symmetrical wing, would probably not perform as well as the Super Cub.
In terms of tail-draggers, Citabrias/Decathalons and Super Cubs are both easy to fly with no vices, although as always, fly the aircraft from startup to shutdown. They will bite if you don't pay attention.
Concerning the Decathalon specifically, I think it is the wrong aircraft if your primary mission is glider towing. The wing is going to give you a longer ground run, but the key point against it is the lack of flaps. Flaps on a glider tug allow you to increase drag after release, thus allowing a decent descent rate while maintaining a reasonable amount of power to avoid shock-cooling.
In a Decathalon or an un-flapped Citabria, you either have to take a long time descending or reduce power and run the risk of cracked cylinders. O-360s are notorious for cracked cylinders, even with careful handling.
A general piece of advice for any tow-plane is that constant-speed props are not required. Fit a fine-pitch seaplane prop and save a lot of money on maintenance. The draw back to that is that cross-country speeds are reduced somewhat.
A final thing to look for in Decathalons is the elevator cables. A friend of mine had a share in a Decathalon and one of his partners discovered one day that he had no elevator control. He landed using the trim, which is relatively easy to do and after landing, he discovered that the battery had been leaking during inverted flying and had eaten through the elevator cables!
