" . . . or what I think is most likely . . . firebox needs more wood . . . I find that while I can have a small fire in the Oslo and it will warm up the house, this stove always seems to do much better and burn better with a full load in the firebox . . ."
Sure . . . pay no attention or heed to FirefighterJake's advice.
. . . I told you that I thought this was the key . . . more wood.
Incidentally, I like Anshenlich1's analogy of the Oslo being like a locomotive . . . I too find it does best when loaded and it takes a bit to truly get it up and running at full steam . . . but then she will really haul and do well.
Oh yeah . . . about the doghouse . . . I tend to pull away the coals from the doghouse and pile on top or slightly in front of the doghouse . . . you can also load this stove right to the gills . . . but any wood too close to the front may roll up against the glass . . . which can lead to the glass blacking . . . or you can get a build up of ash there . . . doesn't affect the burn . . . just a bit unsightly until you sweep the ash off the lip or get a hot fire to burn off the black.