Greetings NBfrost.
Here's what i used to do for my outdoor years ago.
I'm a rockwool man, have few troubles with it.
Compact, good medium, familiar.
But you'll want to get them in soil before going in the ground outside.
Once my gals rooted, i placed them over cellpacks filled with potting soil. Get some thin, but hard plastic.. something, and cut it into strips just thicker than the cubes. I used lids from my long rubbermaid tubs. Cut slits in the strips so you can fit them together, squaring off each pack site, like how pickles, olive oil, etc, are packaged in their boxes.(hope that makes sense to you ;)
So now you have the tray with plastic strips separating each site, so you can fill em up with more soil. Try really hard not allow gaps between the plastic strips and the tray, or roots will grow all into each other, forcing you to tear each clone from the tray, instead of sliding out perfectly.
This method allows you to still root in rockwool, get them used to soil and gives you about 4"s of rootball to plant in the ground, all while still keeping 50 to a tray....
I suggest you throw them outside or under an HID once they're in the soil packs, as you'll need to give em a lot of light for that density of plants at that age.
It works wonders!
Good luck!