I'm not sure if you use a fan speed controller, but if your fan exceeds the carbon filters performance cfm you will need one. For example, I have a 260cfm 6" Fantech fan, static resistance may subtract 40cfm, that leaves me with 220 cfm. If I use a 200 cfm can33 carbon filter I will need to throtle back my fan by 20 cfm in order to not exceed the carbon filters specifications.
I usualy do not like the idea of reversing the carbon filter for the simple reason that it voids the prefilter. This will cause a significant static increase over time due to clogging. I guess you could do it if the fan was strong enough to overcome the static resistance, but it would surely not be eficient in the long run.
Good luck mate!
Unity