Damn, not really familiar with the 8", but unless you are flowering tomorrow, I'd probably go with the 3 gal. It'll last you a few weeks, then transplant into the 5 gal a week or two into flower. It'll help avoid the problem with leeching out buffers and ph drop mid to late flower. The buffers are good for maybe about 6-8 weeks.

I'd get that screen going soon. You'll notice that the sooner you can get the branches growing up into and then along the screen horizontally, the more growth shoots and bud sites you will have. I even tied a few branches so that their lower middle nodes were tied up against the screen, and the new shoots at all the nodes above it were on level with the screen and directly under the light.

I also tuck the fan leaves underneath the new shoots and out of the way every day to two.

It won't look very pretty at first, but in a couple months it'll be a sea of buds :rastasmoke: