fire level in burn pot and heat exchanger

[GreenRoofAcres]

I have an American Royal 1020 (Universal Grain Burner). The fire pot is feed from the bottom up, in the pot there two rows of holes for air. The upper row is about 1 inch from the top and the holes are spaced about 1 inch apart. The second row is about three inches lower with the holes spaced about 3 inches apart. Where should the fire run in relation to these holes?

Another question is the fire chamber heat exchanger, are these custom made by each manufacturer or are there companies that make and sell these types of heat exchangers?

Thanks
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