Well, a lot of times the 'V' shaped firebox causes problems,, A well designed firebox for burning coal has vertical sides or nearly vertical sides.. The problem is that coal has at least 10% ash,, and as the coal burns,, the coal bed settles down with a tapered 'V' firebox, the coal and ash get compressed together as it settles,, this causes clinkers. and the concentrated ash on the grate can cause airflow problems..
I built my own boiler using the 'V' shape,, and regretted it.. If I were to build another hand fired stove or boiler the sides would be vertical, and the firebox very deep, so I could easily have a coal bed that is at least 10" deep.. this is what anthracite likes.. a deep fire with vertical sides..
Do a search on the forum for US stove, and wood coal combination. You will find several threads about the frustration some members have had burning in these type of stoves..
Your particular brand, I don't think has been mentioned on the forum before,, maybe the smaller firebox will work for you.