Coal Bin Design for an EFM

I'm updating this thread and knocking on wood. No jambs so far. Started burning in late October. Also taking Rob's advice I'm have reduced my feed rate and temperature quite a bit. This year I've been running 3 teeth and 3 1/4 air and set my water temperature to 170. The house has been consistently warm and plenty of domestic hot water. When my primary heat zone (forced air water to air heat exchanger) is on and the indirect water heater calls for heat the boiler temper will drop into the 150's but no lower. My previous Harman stoker boiler would keep plummeting and would really struggle to recover. Wish I had found this boiler years ago.
By the way I was able to get 5 3/4 tons into the bin using the window and the 4" pipe method. I bought 6 1/4 tons so I've got a half ton in reserve.