Is it swollen or is it sucked in?
If its swollen you have more air going in than air going out, and if you use a carbon filter this is bad because smell can escape from other places due to positive pressure.
If its sucked in then its all good, if your worried about reduced space just add small buckets or big cups on the sides to create some more space, this is how i do, check out any of my recent diaries and go to the last picture to have a visual look.
Stay lit.