If its of any interest I,ve used both bottem and back blast fires over the years, my current forge is an Alcosa with a back bosch tank and water cooled tue iron never had a problem with it not getting up to heat using breeze coke just use a deep fire if its heavy stock and make sure to clean the clinker out at intervals as not doing will rob your fire of heat . The old industrial forge I got my fire from had cast body fires with up to six tue irons for shipwork they made anchor chains and such wish I,d took the time to photograph the old place as its now gone