I've seen that bulb online before... But everywhere I check it's listed as "out of stock." BUT, as soon as I can actually find a place that has them in, I'm definitely making the switch.
So I've been getting ready for my next grow, and what I'm planning on doing is growing 8 lollipops, each in a 2-liter bottle. I'll trim them just to each be a single, giant cola on each of them. So in that case, I could probably actually squeeze in a ninth plant. With eight, however, I can give them a bit of space around each bottle/pot.
With SCROG the problem really is just trying to find pots that hold enough medium, and that don't take up the entire space of the tent. I've seen 2-gallon "perfect pots" that were 8x8. Maybe you could squeeze in three of those, and let each plant grow to till the screen. The three-gallon bucket was more than enough to support the LA Con clone, which grew to take up the entire canopy. So a 2 gallon bucket should be fine, especially with another plant to fill the space.
I've seen someone do one massive plant in a DR40, in a five gallon bucket. He managed almost 2 ounces dry off of a prodigal yielder.... pretty damn good considering he was using CFLs as well. So you could easily go with one plant, but it would take longer to fill the screen (I've thought about doing this exact same thing... multi-plant scrog).
Keep an eye out for my next grow journal--coming soon--it'll have eight plants, SOG. It should give us both an idea of what can be done...