I've been making them for my own surfboards and windsurfers for a few years, I started copying the ones that the water skiers use and I incorporated the two foils into one shape. An integrated single foil has better pitch control so you're not constantly keeping an eye on the nose and I've built surface piercing foils so they lift as the speed increases, I found a larger foil lifts easily but as the speed increases it gets a bit sensitive so the foil rises as the speed increases and reduces the planing area.
The surfboard foils are different because they water flow comes from across the foil so they're a different design altogether with two levels and shorter struts, not a perfect design yet but it's getting close, the foils lift as you drop into the wave and they're fine for bottom turns and cutties but not too stable in the tube. It's a totally different set of angles and flow in the tube !
I've made about 70 foils over the past 9 years, mainly out of fibreglass and epoxy resin but also out of ply and carbon fibre and some in Aluminium.
Theyre just a variation on what other people are using and I was hoping there might be someone else making their own too.