if he got the right sized pots(maybe just two 10 gals with 2 plants in each) he could pull it off, extensive training with scrog and as i mentioned trying to make the canopy more like a stadium/vertical grow would give him more space for each plant. the right strain would make it a lot easier, and a short veg time(but it all depends how the strain stretches and how long it takes to grow under these conditions).
10 gal is ridiculous, lol- you could grow a 6' tree in a 10 gal. Unless you veg for over 2 month you not going to fill a ten gal. If you veg for two months, your gonna have a tree that is way to big for the space. If you don't veg long enough to completely fill the medium your wasting time and money- you containers won't dry out fast enough and you'll end up watering like once a week! Less watering/feeding=less yeild.
It is doable using bigger containers, but that's a lot of 'technique' for a newer grower. I have 5 in 4 gal. and one in a 5 gal. (6 total) in my 4x4 tent and a novice probably wouldn't be able to fill that much medium with roots and not out grow the space, my tent is wall to wall and super crowded-if my environment wasn't perfect it would be a reciepie for diaster. It takes a lot of training, manipulating, and skill to do it effectively and efficiently, like you mentioned^^^(utilizing multiple training techniques). You could fill a 4x4 screen with one plant in a 5 gal. You would have to veg well over a month(more like 1.5-2 realistically) to actually fill the 5 gal. containers, so without lst, topping, tying down, and a longer veg 5 gal is over kill.
The other benefit of using smaller containers for a new grower is it allows for more frequent watering. If the root mass doesn't fill the medium it takes WAY longer to dry out which means less feedings and waterings wich equals way less growth and reduced yield.
I wouldn't consider using anything over a 3.5 unless you plan on vegging for over a month and a half.
Screens are best left for 'familiar' strains, meaning it's risky to do it with a strain your not familiar with, or have never seen grown before. A hermie or nanner in a screen is a bad scene, lol. Also, without knowing how much a strain stretches a screen can easily get a new grower in over their head. Not to mention not being able to move the plant. I got love for scrog, but I think it's better left for growers with at least a few harvests under their belt.
Smaller containers are the way to go. I regret using bigger ones this run! It was overkill.
A good rule of thumb is 1 gal for every month the plant will be alive. So if you plan on vegging for a month and flowering for 2, then a 3gal is perfect. If you only doing one plant and plan on vegging longer, then a 5 gal. is the way to go. If you plan on doing more then 2, 2 gal. is the way to go in that space. Look at what other people do, the only people I see using over 5gals are growing TREES.