Thanks Mego. I'm looking at boats at the moment, smooth water type around the 4 metre mark. One I have my eye on is the Anglapro Outlaw 424, packaged with a 30hp 2-stroke. I realise the 30 is right at the low end of the scale for the boat but a step up to a 40hp 4 stroke doubles the price of the donk!
I think there a different plates/foils for different purposes these days TD but all probably originated from the basic cavitation plate principle. I had them on my last 2 boats so I could be on the plane at lower speeds for trolling.