Hey Baz,
I am no expert but i'll tell you how the rig is set up on the Nile Special.
First off, you're going to need a waterski rope.
Attach it up stream of the feature and as far out as possible, idealy you want the fastening point to be in line with the wave - the Nile Special has a pole jutting
out over the water and has been cemented into place. I'm not sure how important this is but it definately helps.
The length of the rope should allow the paddler to sit right on or just in front of the wave face.
Attach a throw line to the middle of the rope so that someone can pull it back to the eddy/shore for the next paddler to use - kind of like a 'T' shape.
Hope that helps,
as i said i am no expert on the matter and hopefully someone
can correct/add on to what i have said.
Cheers
Scotty R