With that setup, 2oz. per plant is reasonable. Definitely get the 5 gal pots, but remember to transplant several times before this. You don't want them sitting in those 5 gals for much more than 2 months, as you will start to have ph problems.

For the scrog, you are correct, it will be difficult to flush them, take them out to turn them, etc. etc., unless you give each plant it's own screen. It would be good to figure out someway to catch water run-off not just for flushing, but regular waterings as well (you want a little run-off each time, maybe 10% of the total water you give them)

If you are planning to scrog, you will also need to do some LST first, perhaps even some topping or fimming (up to you, I don't like topping or fimming because of the long recovery times)

Here's a nice scrog, lots of good info: http://boards.cannabis.com/closet-ca...ly-ladies.html