Fire box finish up

[Kitecop]

I have my first fire box just about assembled. I plan to cut the door out from the inside before welding the rear plate in place. Is there an advantage to making the door shorter rather than the full height of the firebox? My thinking is that a short door will not allow all the heat at the top to spill out when opened to put wood in or when cracked when used as an intake. When I attach the box to the tank should the box outlet spill into mid level or to the lower portion of the tank? How many are using a baffle to direct heat up?