CSM! Cup Size Matters - for the littl'uns

I planted 5 seeds and 9 days ago they sprouted and this is what I have today.
I had only one of the small planters and so planted the others in plastic drinking cups.
The seedling in the bigger pot is now twice as large as the small cup.
Coincidence? Would it be 3X the size in a 3X bigger pot?

Only to a point, and it could just be coincidence.

Hopefully you’ve got some drainage holes in the bottom of them cups.

I personally start seeds directly into soil in clear cups, like you show in your picture. Allows me to see the root structure from day to day. But I place the clear cup in a regular cup, to protect the root system from light.

Yes, I poked 4 drainage holes in each cup