Hello Biggins,

Not sure why you havn't gotten any responces (maybe the size of your proposed op puts some off here) but I'll try to give you a thought or two.

You will be better served using one rez per 4x8 tray. If each tray/rez is seperate from the others there is less of a chance having a problem from one becomming a problem with both or all. An example would be a root born problem like root rot, it would suck to loose a tray's worth of plant material but a bigger problem if you loose 2 or all. Plus there are other plant problems then could be spread by the common resivoir, especially using flood and drain.

I like your idea of using 3- 600w lights for a 4x8 area. This is a lot more effiecent then 2- 1000w lights, not only is it 200w savings from the git go but there is only about 10,000 lumen diference between the set ups and that is more then made up by the better light distribution.

Look to build in redunancy where you can but always have spares of everything handy and ready to go for when something does go tits up.

good luck with it all.