I wouldn't like to guess at the moment what speed it gets up on the plane as I have only been out a few times, and to be honest I am not experienced enough to give an acurate estimate.....doesn't need to be too windy though.

I quite fancy getting one of those GPS systems to record some speeds. It would be nice also to get a waterproof video camera so I can do some recording on the water, doubt I can afford this till next year though

Looking at some sailing videos, I would be interested to know how they incorporate the GPS readout into the film ....it makes for some really interesting footage when you can see the speed readout.