Tony, you have a rather low threshold just inside your doors, you could go to a lumber yard or masonry sales store and buy a couple of firebrick to make a higher front wall so you can stack the coal deeper at the front.
This is what I do in my boiler. I never knew when I designed it that I needed a 18" deep firebox!! I stack three firebrick horozontally, this is 4.5"x 3=13.5" high front wall.
Just be VERY carefull about knockiing the red-hot firebrick out of the doorway onto the floor, first they are hot enough to burn you through leather gloves [don't ask], and second they will ignite any paper or kindling they land on. [again, don't ask
] My boiler is out in an outbuilding, not attached to any other structures. Make sure you have a non flamable floor in front of the stove.
Let us know how you do in the morning. I'm off to load the night's coal in the boiler.