Welcome :jointsmile:

I wish I could answer your questions... but can I make a couple suggestions?

If you plan on keeping the flower room narrow like you said 5'x2.5', you could get the 600w and put in a linear(?) light mover. Otherwise, making the room a little more square would be the most efficient way.

But, why not just split the whole room down the middle? Then you have a 5'x5' flowering room...

As for the area, it's really up to you. Since you are doing Scrog it might make things a little more difficult. I just did a scrog grow (2nd link in sig) with 2 plants and had them in the same screen. Not sure how you were planning your screen, but I'd say having them separate is much easier. But as far as how long to veg, when to put the screen on, what kind of area is best... those all depend on the strain you are working with (if you have everything else right, of course). Some will stretch more in flower than others, so with some you may want to fill 50% of the screen before flowering, and some maybe 70%.

For me, I did a grow with LST first, then with Scrog on the same strain the next. I had plenty of pictures from each week, so I could kind of gauge how much they would stretch during flowering. On my scrog grow, I did a lot of LST during veg, and put them under the screen two days before flowering (the two plants filled up about 60% of the screen).

So, if you LST well, you won't need the screens in your veg room, which would just take up space.
Here's a good scrog log, where I got a lot of ideas from -->http://boards.cannabis.com/closet-ca...ly-ladies.html

Hope this helps a little... good luck :jointsmile: