HOW DO I DETERMINE THE MAXIMUM HEIGHT AND SIZE (DIAMETER) OF A WOOD BURNING PREFAB FIREPLACE INSERT? CMC CHAPTER 8 HAS MANY TABLES, BUT DOESNT EXPLAIN DIFFERENCE BETWEEN VERTICAL AND LATERAL DISTANCES. IS THE LATERAL DISTANCE IN ADDITION TO THE VERTICAL, OR A COMBINATION OF HORIZ. AND VERTICAL (IN WHICH CASE LATERAL SHOULD BE GREATER THAN VERTICAL)?