On some I run 24 from start til the 2nd week of flower then switch to 20/4 til she finishes. I would recommend the same with your hps for veg then switch to mh 2 weeks into flower til she's done. But if you don't want to mess with switching you can run either cycle with good results, this is just how I've personally seen the best results. Keep us posted on your progress. Happy growing!