I grew up in a house, and have seen the term used around here, where you stuff in a couple big "overnighters" to keep the stove going all night long. On the coldest of nights with our F400 trying to heat 1500 square feet I would stuff a few big pieces in around 10pm then when the baby woke up around 3am to keep things in the low-mid 60s (we are used to being poor college students so mid 60s is shorts and a t-shirt attire in our house). In recent weeks I have been taking those big pieces and splitting them into 3 or 4 small pieces, maybe 2-3" and can usually get a third piece split up as well. So now I'm packing the stove with 9-12 smaller 18" pieces. I have noticed there is no point in filling the stove in the early hours and if I go to bed at 67* the house will still be 62-63* in the morning with plenty of coals to get things going with no effort. It's a few more swings with the x27 but no waking up and I'm actually burning less wood. I think with a firebox <2' it might be the way to go.
My experience is that modern stoves make more heat with smaller pieces...don't do as well with big chunks.
With a cat stove, you can fill it with kindling, doesn't matter...but the bigins' seen to burn up less
When I want to fill the stove for as long and hot of a burn as possible, I'll use smaller pieces on top to fill in as much space as I can. But I use big pieces on the bottom, as high as I can go before hitting the tubes.