It's not a "stubby", but I would say somewhere around 4" long? Shorter doesn't gain you much in turnbuckle length, while longer needs a longer turnbuckle. The rubber band is needed to pull the wrench fast to the bar AND when pushed up against the sides of the wrench it keeps it from moving sideways. A set-screw would have been cool, but drilling into a hardened wrench is a no-go.
The center aluminum part of the turnbuckle is 3" (so I guess the wrench I used is 4"-ish) and I really needed a 4" version but that wasn't available at my ACE hardware store, so I opted, instead, to just buy one longer eyebolt (the brighter and longer one in the photo) to extend the reach. Get the wrench on the bar, measure from the other end to the stud and that's the turnbuckle range you'll need.
Teflon tape on the eyebolt threads helped a lot in keeping everything from moving when the engine is running and gives it a nice "feel" when turning the buckle to change engine speed.