I never PHd my rockwool, also just took my SLH cuttings n just dipped em in a cloning solution and whacked em on in. They did want to wilt at 1st, so i put a few matchsticks in next to em to support their weight.
They were a bit of a difficult strain to clone.
Good Luck though.
Also if u want nemore info on SLH feel free to check my journal in my sig.