This is the exact opposite of nature. Limiting root space is not a good thing. Over-watering is always the problem. Not the container size. I’d never grow a seed or clone in a solo cup for any amount of time.

Damn Straight!

Rockwool has a neutral pH of 7. Roots in an inert media prefer a pH of 5.5-6. Soak the rockwool in a 5.5 pH solution for a few hours before use.