1 1/4" vs 4" rock wool for dwc

i was wondering which will do better just putting the small rock wool starter cube in the rocks for my dwc or putting them into a 4" then into my mesh pots. i didn't know if the bigger one would make the stem rot with it constantly being wet or not what do you guys think ill be using 5" mesh pots in a 2 gallon bucket

Use the smaller cubes, they are just a starter. This will leave more space for your grow medium in the mesh pots. I use 1.5 in 4 in pots.