I was blessed with my McTavish EvoII from Asea. There's a little mark as to where to place the fin. Came with a lovely fin set-up. FCS Fluid Foils Dolfin & McT side bites. Usually it's the other way around, McT Single, and FCS GXQ side bites.

Base of fin is about 5"3/4.
Front of fin from tail is about 1 foot plus 2 & 5/8 - or about 370mm.

I reckon a smaller back fin and bigger sides would liven it up a bit more.
Well worth a try.