I have tryed a few different sized bubble pots, the genral rule of thumb for soil pot size is about correct, 5L for a 12/12 no veg, 10L few weeks veg, 15-25L 1-2 month veg. I once kept a mom in about a 60L big black bin for 5 months It looked like a small tree, trust bigger is better!
10L should be fine, it's TWO times the size ya did use and ya found that ok. Also a few times I have used a header tank and a pump in bubble pots to increase rez size ya could use to avoid cutting ya shelf if ya got a little water pump spare? but I would use ya 10L tubs myself for root space.
In that case I'll stick with the 10L rez-tubs and re-mod the shelf, it'll be a while before i get it done now though, unless I can borrow a drill off a mate in a hurry cos my last one set on fire lol, whilst cutting holes for the 3 fans

anyhow... I use a boat engine-cyphone? pump to do my water changes and top-ups, I'll post a pic of that to avoid confusion in a bit

That's a real good point actually about the C02 in my last unit I was only running CFL's AND LED UFO's so heat wasnt an issue...I could have the main fan turned off for for 30mins every morning (lights on) and the temps would not be an issue then the main fan would turn on and within a second or so the room was back at 26oC. I can now see that this is and will be an issue, can't believe i overlooked this important detail! the 600's heat is fucking mental! I can't see away around this problem any light on the subject or creditable info will be greatly received + rep many thanks - STELTHY