Vertical Forge

I have a question about something I saw in this month's issue of Blade Magazine. Instead of the usual horizontal position, a forge was set up vertically. A comment was made about the forge likely being more fuel efficient in this configuration, and it makes sense to me. The part that concerns me is the vortex effect. In a cylindrical forge configuration, wouldn't the center be 'colder', with it getting 'hotter' (into the main of the swirling gases) the farther from center you go? If I am correct, I would expect the using a vertical forge would create hot spots on the billet ends. Anyone have any experience in this area? Thanks.

Brett