I'm not familiar with Stonington blend at all but as long as it has a good calcium additive along with a full mineral spectrum and good carbon, whether that be coco or spagnum peatmoss, and a good pile of perlite in it then it will work. If it comes dusted with myco thats even better. I started out by buying a soil called Bluesky Organic Supersoil, it worked excellent, then I spent 3 years trying my own blends only to end up back at Bluesky because I couldn't really make it any better, only cheaper, but not that much cheaper, and its a ton of work. All I do now is run the BS supersoil thru my wormfarm to make my own EWC. Then I add 1 gal of coco per 2 gals of ewc and 1.5 gals perlite for 4.5 gals and add another 4.5 gals of BS Supersoil for a total of 9 gals and then I uppot my 2 gal veg pot into that in a 10gal pot. It leaves a bit left over which I usually add to my next tray of EWC. I have grown beautiful plants in straight store bought Bluesky soil many times as well but get better results with the EWC. When you make EWC all the myco in it is destroyed by the worms so you need to add extra myco at each uppotting by dusting the rootball. I would imagine stoningtons blend is very similar to Bluesky. The key is not having really strong soil but having a complete soil and then upping the pot size so the plant has enough food to make it through. 6gal cubed smart pots that fit in milk crates work excellent for clones but plants from seeds need a bigger pot or else you end up flowering the plant too young. I find 10gal pots are easy and bullet proof plus when they are deep into flower they only need water every 3 days. 4 10gal pots hold the RH in my tent perfectly for VPD to be optimal as that extra moisture allows me to control VPD by venting moisture out with an inline fan instead of trying to add moisture. I live in a desert so its dry here. The worms eat alot of the carbon and the added veggy scraps make the mix gooey so thats why I add coco, to replace the carbon, and perlite to cut the coco and offset the gooey.