I have a Van Wert OCF/HF 120 and used to use it before I got the new Keystoker. I have not use it with FHA. Here are a few cautions:
1. It can burn wood but it won't do it well. The water jacket design keeps the walls too cool to support complete combustion. You'll get lots of creosote.
2. It has a huge firebox which is great when its really cold. But when you get nights in the teens and days in the 40s, it is a curse. With barometric and thermostatic dampers, it will clamp down when it gets warm out. But enough air will get in there. The temp will slowly rise all day (and the chimney will smolder). You will need to be able to dump that heat somewhere. You will need an aquastat that makes contacts with temperature rise (maybe190-200ish). That aquastat needs to signal the system to turn on. You could easily find yourself opening your windows to cool the house on such days.
3. Be careful about opening the door soon after fresh coal has been added to an established fire. The inrush of oxygen into the superheated methane can quite literally blow up in your face. Use the make-up air vent first.