Oh and by the way my proposed cut is 30 cm long, into the board and 20cm wide at the back which is the widest point,
bare in mind the board is a semi wide 161.
How does that compare with the cut on your 172 supermodel?
Mine is 175 wide at the widest point and about 300mm deep from the end of the tail, the board has a tail width of 304mm. More is better as long as you dont lose strength chasing those last few mm. Yours look good in the pic with the full depth template, run with it.
Ps watch this vid, at 0.15 watch me stand on the tail to avoid that tree, if I werent on a swallowtail I was hitting that tree bigtime.