2:1 coco to perlite -- golden. ~30% perlite
Fertigate every irrigation around 1.3-1.5 concentration with a well-balanced feed and it'll go fine. Dial it in and you'll have a 2' 40+ gram solo cup plant no problem.
the goal is the plant gets so big oyu need something to hold the cup upright because it's so top-heavy :P
and think about how you'll secure it when it gets there... so ti doesn't fall over.
I always rinse my coco to get the smaller particles out of it. Then soak it in 150 ppm of cal/mag for 30 min. Growing in a solo cup i would only add 5-10% perlite.