I too have recently gone back to wood. I don’t have a lot of experience with it yet, but here’s what I can say.
Firstly, Ashby says that the most important factor for good penetration is weight. 650 grains minimum. So I take that as the guiding principle.
Secondly, You an do some stuff to increase your FOC, like tapering the back of the arrow.
So I have tried several hard woods but ended up with douglas fir shafts in a about 70-75 spine range. I think they are around 29″ BOP and I have a 200 grain point on them. (190 grn with a bit of lead added). Total weight about 650 gns.
I will either tip them with tough heads or abowyers to hunt with.
You can get spine weights as high as 100 from surewood shafts. But chasing high FOC with wood is a fools errand.
My advice is to build a heavy strong shaft that will shoot at least 160 fps and flies straight and true.