GrowRoom GL120: Where should I set up fans and filter

I'm about to purchase a GrowRoom GL120 tent(4x4x7), with a 600watt mh/hps digital electric ballast with a 6" cooltube, 6" GrowBright High Velocity inline fan w/ charcoal filter and a 6" inline duct fan.

I made a diagram of how my setup will look like. My question is:

1) Should I use a smaller 4" fan (170cfm) instead of the 6" 424cfm fan?

2) Where should I put the charcoal filter? Should I hang it, put it on the floor, or put a empty box on the floor with the filter on top?

3) Where should I put the temp. reader to make it more accurate? I read that it shouldn't be below the light so on the diagram I have it at the top left corner.

4) Should I add anything else?

Thanks for the help.

1. Get the 6" and use a controller
2. I'd run ducting from the open flange on the hood down to a filter on the floor.
3. At the plant tops but out of the light to keep radiant heat from skewing the reading.

Let me know how that carbon filter works for you. I still need one for when I get further along and the price is reasonable on those.

Thanks Sick. I will try it like that. Thats what I was thinking I would do. I will keep you updated on the charcoal filter.