Coal and Wood Burning Fireplace Insert

I own a Vermont Castings Vigilant 1400 with short legs in my fireplace, which was sold as a “multi-fuel” (wood or coal) stove. The manual describes going back and forth, but I find that burning coal exclusively is far mor practical. Having said that, if I remove the ash pan and shaker grates, I can lay a wood fire on the bottom of the stove (insulated with a couple of inches of ash), and have a very respectable wood stove. I open the over fire air inlet too. I only burn it this way in the spring when I want to take the chill out, and the byproduct is a creosote coating to the stove interior and the chimney liner to protect it for the summer. The liner was left over from my woodstove days, and is doing very well with this protocol.