how tall r the cuts. good rule of thumb for me is stem 2 inches down under neopremes in machine and 3-5 inches on top of machine.
not sure about taking out of rock wool, but if those r your only cut i would for sure give it a try.
45 degree cut 3/16-1/4 inch below node, scrape 3/8 -1/2 on bottom exposing the cambium, dip and place in machine.