Kinze 3600 Pneumatic Down Pressure Bags

We're looking to add some automated down force to our 16/31 3600 for next year, ideally we'd go Delta Force or something similar, but that just isn't in the financially responsible category for the amount it acres we farm. I think an air bag setup would be a good halfway point, our Precision dealer says that Air Force is only up pressure on the 3600s, which we don't even need. I know that Kinze's factory/retrofit kit has down pressure. Reviews on other forums seem really positive on them. Anyone have any experience with them, and more importantly: did anyone add Delta Force or hydraulic and want to sell their air bags?