Luverley!
. Can you dye this stuff nicco?...
BB2K, what is making the water 'curl under' in your pic on the last page?. the way I see it there would/will be a dead spot there(that will curl, but on itself). imagine driving a car over a surface like that both ways, the way it is now would be smoothest, the other way will be more 'turbulant' (and slightly more 'restrictive'
)...
I'd try a smooth one and beadblast it. maybe try one with lines 'spoking' out from the centre with some fancy dremel work, or scored with a sharp blade?, to increase surface area...