I just got the same Harman stove installed last week. I find once I load the hopper I take my hand and push the pellets to the back and up as there is a lot of room in the upper back top portion of the stove. It seems to leave an empty void if I don’t push more pellets up in this area by hand. Just what I observed. Love this stove and I am very happy with its performance. Since it was installed my gas heat has not came on once in my 2200 sq foot home!!