Young (small) root systems are easily 'drowned'. Keep in mind lava rock drains very quickly, BUT, has lots of tiny crevices which hold a small amount of nutes in reserve, which hungry roots can draw from in between feed cycles, BUT, they are not soaking in it, like they do in rock wool/S2G... AND clean up is a snap + they are reuseable oh, and very inexpensive. Like hydroton, LR needs to be pre-washed to remove grit that can clog your drain return to the rez.
My pvc tube feed system is not glued. I swap out pieces with more or fewer mist heads to assure adequate coverage throughout the lava rock, thus avoiding dry spots. This, combined with a small pump, provides a 'perfect' combination, essentially turbocharging/supercharging the grow.
My timer is analog with 2 knobs, so I watch the flood and cut back once I feel the LR is sufficiently wet
During early veg I lower the on time and increase the pause time.