Righty-o, I didn't notice before but Can Filter lists the max cfm rating for the different filters.
Can Filter 705: 13 cfm max
Can Filter 2600: 46 cfm max
The 705 is a lot smaller, I'd prefer that but I'm not sure if it would work as 13 cfm seems really low. My box is 10 cubic feet. Im wondering if an exchange of all the air in the box each minute would be enough to keep humidity down. Also at such a small rating would assume it wouldn't last that long.
Can Filter 705: 0.5kg Carbon
Can Filter 2600: 2.1kg Carbon
Decisions decisions. The small filter I could fit outside the box, the 2600 would have to go inside.
Edit: my drawing above shows the 2609 would fit outside, I'll have to double check that tomorrow when info pick up more h2o2 from the grow store.