I've had the same problem, came up with the same solution in my mind, and got just as far as you in making the solution a reality  :cboy:

Instead I end up taking a cotton rope pigging string and hogtie the little devils. I've gotten fairly handy at tying the slippery little devils too  :cowboy:

I also find that the longer the tow rope on the sled the better the momma will follow. Some can be kinda shy. It also allows me a bit of a head start if momma blames me for the situation.