I haven't tried it but even my MH on its own is to much for beanlings to early. If I had the space & cash I might try using both as I have read it is the best possible option for HID use. But I believe it would be a matter of balance rather than just equal amounts. For example if I was going for it I might try a 250W HPS with a 400W MH on either side for veg & the reverse for flowering. From the growth I have had using MH followed by HPS I would want a lot of headroom if I was going to use HPS from the begging of veg. Hopefully you will get someone who has tried it & they can give an experiment report. My idea will probably be wrong so no worries I won't be giving it a bash for a while.