hey Edskins if you try a coco perlite mix, id say just mix it yourself, and the more drainage the better, if you think youve put in enough perlite, put in some more because as you mix it with the coco it dont go far.
the resoning here is weed roots need to breath, not be sufocated by too much watering, thats when you will see yellow leaves apears, so as long as you got good drainage your weed will luv ya, ive even seen 100% perlite hydro grows, but thats crazy,
just mix heaps of perlite with whatever coco you can find, and start feeding (by hand every two days when seedlings, no pumps) with a coco formula at the mmls suggested on the bottle and come harvest time, you'll have a grow to make the pro's jealous... best of luck