There was a short story about two college guys who're spending a break helping out on the farm. While the rest of the folks are gone for the day, one agrees to help the other fulfill a fantasy. In a hiding place in the hay bales, the one guy is tied and suspended by baling twine around his nuts. At the end there's a hint of a possible follow on (one I don't think was ever written) as the guy mentions he's wondering about the elastrator. Anybody recall the title or author?