That's where a radiant heater is most effective. That's precious space on most boats under 40' and Alden found a good niche on my boat. It's out of the way in it's sleeping mode while sailing and in warm weather. But when it's fired, the heat is down low where the heat and flicker of the flame is most appreciated on a cool Maine evening.
There's a cast iron plate cover that fits above the grate but it's removed for the photo. It's a little scary like this.