Rockwool question

Hey I'm looking to try rockwool for my autos does it matter how big of a cube I get? Can I start off with a big cube or does it matter?

I haven't tried to start off in a big cube only starter cubes, but I think that your plant will develop a better root system if it the cube almost dry out before next irrigation. Also smaller cube means less risk for drowning the plant.

Rockwool has a major flaw whereby it holds to much water which effects oxygen levels, therefore starving the planet and creates many other issues,
Root riot plugs or Eazyplugs will work much better in my opinion. Pop the seeds into 1/2" plugs /cubes until roots are showing, then into 3" plug and off you go.. good luck dude

I used a quite big rockwool cube and it worked well. The only thing you need to consider is that the top of the plant take some days to pop up on top. In my case it took 6 days from planting and this worried me a little bit. The root appears on the botton a day before.
In the picture the plant after 6 days of germination.

I always started in a macro plug until it rooted. Then I put it into a 4x4x2" cube. Then you can sit it on top of a Unislab, a regular slab or 8x8x8 cube. The bigger cube will wick the excess water from the smaller cube, making it almost impossible to overwater. Plus it will be a transplant without any of the shock.