i think you are going to need a better fan. with thhat much light, plus a carbon filter, i dont think a PC fan would cut it. Id suggest a 4" vortex fan.
also, this is just my opinion, side lighting works for big big plants. in cabinets, i learned, light is more effective coming from the top, saturating the canopy rather than the tiny lower bud sites. If you can fit that much light in the box, you are better off having the light at the top in order to get as much light on the canopy as possible.
to me, it doesnt make sense to put lights all around the sides of a box when that space can be utilized to grow a thicker canopy, with the light source(s) at the top.
If you are groing in a box your plants aren't going to be tall, so keep the light above in order to promote bushy growth.
and a canopy doesnt have to mean a SOG or scrog. If you dont have a canopy of green in any grow system you simply arent utilizing your space well enough. thats just thhe way i see it
its all about getting as many colas as you can packed into a tight space under the lamps
LST is a great way to increase bud sites, thus making a nice canopy.
are the fans in the bottom corners for intake?