I've started adding coco after killing my last two seedlings by burning the roots... ballpark my recipe is this:
45% FFOF
30% Coco Coir
10% EWC
7.5% pumice (fine grade)
7.5% biochar
Trace amounts: Mykos, mosquito bits
I'm using that for 1 gallon pots/my first transplant.
Might up the ratio...