25cm rear, 10cm front
My guess is board will not track as good with only rears, need more rear foot pressure. Did not have chance to try it before buyer picked it up.
According to theory, Canted fins allow board to be looser in turning, so by canting big fins you get good tracking and upwind abiltiy and somewhat loose turning.

TFC fins are so expensive, i´m thinking of getting a 3-d milling machine and making them myself, and others.

I would sugest you to make mold out of original and than make copies, cheaper, but with little quaity loss. TFC is makeing theif fins out of G10 this is heavy stuff for a tool (router bit).