RE: Fin for KidsPro S-Type as Speed Board?
I am only 74 Kgs and 5'10" and I found assymetrical speed fins between 19cm and 22cm worked very well for me. For your size I would think the 22 -24 range would be the go in Assys and 25-28 in Symmetrical. One thing I did find is that the board was smoother and more stable with a raked fin or a normal raked TM45 20cm fin set further back on the box. Because the board is quite short you will need to be well powered up to get going but this board has huge potential on good flat speed water, more than I have tapped so far at over 42 knots. TM45 22 or C3 raked would be good, Techtonics 26-28 in symmetrical slalom type. The footstrap stance is closer than conventional adult slalom boards but I actually think this an advantage. The strap positions are also a bit closer to the rail for big feet but I also like this and just run the straps a bit bigger with my feet further in.
Hope this helps
The older I get, the better I was.