I agree with the 18/6, I have tried both with clones and some sprouts. Most plants do most of their growing during the dark period where they expend the energies stored during the light period. Root development also seems to occur during this dark period. The best advice I can give is to actually try if possible a clone from the same mother and do one at 24/0 and one at 18/6 and see which you think is the healthiest and happiest plant. Granted this is more work and involves more intense scrutiny of your plants but until you can see the side by side results you will always wonder which is best. Good Luck and let us know which is best in your opinion.