Have not been able to prove this out on a grow...tried 2-600watters HPS and a single 600 MH and my yield was a little smaller 3 oz's per plant...but no two pheno's are the same and there were other influences on the grow....but certainly don't feel it is necessary....I do believe you as I have read all the studie's....just in practice not proven...I do not like the dual lamps I am an engineer and feel the mix is not evenly distributed with my xxl hood's....When I put my lux meter in the space it made hot spot's and did NOT blend well! w/1000 dual arc the lumen's at 1 foot went from 86,000-120,000 (sylvania 1444) my luminex 1000 watter is 155,000 at almost all location's varie's 5-7% no hot spot's! If you use give me your reading's and your yield statistic's per plant per grow if you can I would really apreciate it! not locked in my thinking just careful with change until proven thru application (don't care about what is said to happen I live in the real world not a lab!)...I've been growing over 50 year's and feel my openion's are valid...wishing you the best with your grow my brother! and if you have first hand info I will be very pleased to talk to you as I have gone down this road in the past with no difinitive answer's...allway's room for improvement!!Thank You jack