I use the 1" rockwool cubes to start my tomatoes every years never had any problems. If you want to get big healthy roots before transplant to dutch bucket you should build a small
aeroponic cloner for use with seedlings.
You'll need a black tote box similar to this.
2 inch net pots
These red 360 degree sprayers
I use this timer for my dutch bucket system can also be used with the cloner.
You would also need some hydroton to fill in around the cube. You will also need 1/4 PVC piping.
Depending on how many plants you want would determine how many holes you would drill into the tote box.
You will have to set up the pvc piping and use a tap to insert the 360 degree sprayers with water
pump inside the tote with water and just a little bit of
nutrients added. The ends of the pvc piping needs to be sealed.
The roots will grow very fast using this set up. You can take the plants including the 2 inch net pots they're in and transplant into the dutch bucket as is just cover the top of the net pot with the perlite in the dutch buckets. Use the same watering timing you were using in the cloner for about a week then you can adjust as you see fit.