Is it possible, how, and does it work?  Anyone done this before?

I mounted mine without a kit. They way I mounted it was drilled a small hole in the bottom fin of my troll. motor and bolted the transducer to it. it has been on there for 2 years now and no problems.

I took a 1" wide piece of steel, about 8" long.

Drilled 2 holes in one end to mount it to the shaft of my motor using a small muffler type clamp and some rubber hose as an "insulator" from any vibration.

I mounted the transducer to the other end of the metal using the actual tranducer bracket.

Works great and doesn't cause any noticable rotational twist.

Depending on the type of x-ducer a 3" hose clamp might work. Expoxy the hose  clamp to the top x-duced. Fasten the hose clamp aronnd the trolling motor. By the time you get done with all that you can buy a bracket for under $20. I think I saw one at West Marine for $11 & change. If you just got your depth finder & have not used your x-ducer most companies will trade you out if they make a trolling motor x-ducer. I know Garmin will.