from what i have read, trust, i have done a lot and i mean a lot of research into which soil i should use. Im not down playing FF as a bad product because of everything that i have read, i have probably a 50/50 like/dislike of FF. Also, i have read great stuff about growers making their own mixes using fish meal, blood and bone meal, microbial life, myccorihizae, peat, dolomite, perlite, vermiculite, alfalfa meal, feather meal, and the holy grail of soil amendements **WORM CASTINGS**
What you are better off doing is making a grow with two same strain plants, same light schedule, and same TLC for each one in FF and another in your own homemade mix of soil with any of the aforementioned soil amendements and gauge your success with each, jotting down new growth each day or week, stem thickness and all that good stuff.
then after you have done your research and experiment, come to a conclusion based on your findings as which one worked the best.
hopefully that helped some