Space and footprint are an issue for me since my flower room isn't too big...I also am only running the TGA base as of now, but plan on doing some ladies in ss in 7's!!
As "they" say....I heard that... I have a 4x4 tent I use for veg and a 4x8 tent for flowering... It works but I need one more smaller space for cloning and seeds when I do so because trying to clone and veg in the same tent is a real bitch... Also at the moment I cant run both lights in my 4x8 because of my power issues so thats a complete 4x4 being un-used, hurricane sandy took out the panel which the main feeds to my grow spaces' sub-panel were wired to and the people making the repairs think my grow spot is just a dead space that doesnt need electricity or heat at the moment so its gonna be the LAST thing they do..... Talk about a catch 22.... Even before the storm and all my equipment was hooked up properly I was just starting to get everything working properly and optimally, now I'm like a 3 legged dog with a broken foot and a cinder block tied to my waist....
But for the OG poster... I think 7gal pots are enough but its all about what your growing above it that makes the call, if your gonna grow some 6+ foot monsters... you may want to up that pot a bit.. 10's as the others said can create some giants.. But bigger root equals more/bigger fruit is definitely the truth.. On my first grow I put a plant in a 10 gallon rubbermade container and that thing ended up being like 7 feet tall under T8's and CFL's by the time I had to get rid of it because it was just too big for me to flower (I was waiting for my HID lights before flowering and it took a bit longer than expected)... But I think for scrogs... depending on how big but something like oriah does... should get a bigger pot just because its gonna require more veg time than a normal plant, I'm not sure what size he uses but I'm guessing at least a 10 gallon smart pot.... Also... smart pots can be sized down... not that you should because bigger/more roots are always gonna give more, but if you HAD to... you could probably grow the same sized plant that would require a 7 gallon hard pot in a 5 gallon smart pot (or anything similar) due to how they force the roots to grow... But if your gonna grow single cola plants as quick as you can.. you could probably get away using a 5 gal or even a 3gal smarty using supersoil backed up with teas and/or organic nutes...
It all comes down to how you want to grow and what works for you.. We can all tell you what you wanna hear but when you get that monster of a room up and running and see for yourself how everything is gonna work, you'll figure out what you need... Personally, to start..... I vote for 7 gal smarty's...