Can't believe the century 2500 is 4 yrs old. I knew going into it the box is small and it was ok knowing I need to reload once every 2 hrs or so. Based on the fireplace dimension, there are a couple inches wiggle room to get a slightly bigger unit, maybe a 1.8 cu ft insert. Maybe I can fit one that's 3" wider, taller and deeper/sticks out a little more outside the cover then again, just by that estimate I m not gaining much volume/less reloads. What do you think?