Here's the deal, from my perspective at least, and I m stoned... FFOF isn't exactly like your quite strictly soil-less mediums that dominate the market: Roots Organic is quite soil-less, Light-Warrior, Happy Frog, Pro-Mix, Sunshine Adv. and most related products. These are all sphagnum and/or coir based with perlite, pumice, perhaps some earthworm castings as with Roots and HF and what-ever other ingredients. There is no soil in those products.
But there is soil in FFOF, it is listed in the ingredients as 'sandy loam' (loam characterizes a soil with a certain even proportion of sand, silt and clay). Of course there is still sphagnum in it as a conditioner, and it was designed before coir became the amendment that it is. Ocean Forest also has forest humus, earthworm castings and another form of compost... it is just loaded with organic matter.
So if you take Ocean Forest, mix in high-quality coco coir at perhaps 25-33%, maybe a little bit more perlite and 1.5 tbsp\gal dolomite lime it should be just fine. More recently trying 1 tbsp dolomite + 1 tbsp Azomite.