I would pay the extra and get them to spread it with the spreader truck. By the time you pull the buggy to the field, then have to hook up to the tractor, spread, and then have to hook back up to the truck and haul it back to the Co-Op you aren't going to save anything. Don't let the spreader truck or buggy go down hill in a plot unless the soil is firm, when they get stuck you have a problem.