Hi there ! 1st before answering I'll give you a free advice : if you use a 2 part nutrient then use the 2 parts , your infos says you'r using only coco B instead of coco A+B. 2nd I think you can use a coco nuts in soil but I don't think it will provide everythingsyour plants needs , as coco requiere much more Cal Mag their is a CalMag excess risk. Now according to me you can find shorter strains in the indica pool or you can learn how to keep you plant short with LST or HST or direct 12/12 , any height controle method , it will allow you to grow any strain you wanna test ( sativa's are a bit tricky to keep short but some can , like the Amnesika 2.0 from philosopher seeds ). Hope it will help you 😁👍