Thanks very much, Gav and Chris for your most useful info. I've also been in contact directly with Dave Bullock who says there is a significant reduction in performance with 4 blades. Our Super Cub came from Booker a few years ago. Unfortunately at Ringmer we had to borrow Nympsfield's Super Decathlon recently and the locals noted that it was significantly quieter. Of course the performance was not as good. We also had a trial of the Eurofox, which they also cottoned on to and are now expecting that we can do something about the noise. Although we have 800m at Ringmer there is a significant slope. The Eurofox had acceptable takeoff performance downhill, although the tow times were doubled - in fact one student pulled off at 1500ft thinking they were at 2500ft! But it would definitely be out uphill in a north easterly. It's a difficult problem and I suppose if anyone had found a good solution we'd all be using it.