Can't find a difference that explains almost .4 w/kg. I do have gear weight at 8 because of helmet and shoes etc. That could be 1-2 % difference. I do use potential energy instead of calculation via force and angle but have tested it and it does not change the result.

Wrote some code and this is what I'm getting. This agrees with my usual estimates(I almost always get etalon 0.1 - 0.2 lower than Naichaca, probably something with the assumptions)

Yeah maybe as an estimate you could take the straight line from start to finish, and modify the wind with this, then you correct for parts in different directions. Added some pictures (trying) to illustrate it.