It would be a real gas hog!
That's a pretty large area to get up to forging heat.
When you get a piece of steel red, you are at around 900-1000 degrees.
You are only 1/2 way there.
When using the forge, what you have done first is brought the entire mass of the forge up to around 1800-2000 degrees for forging heat and you are working on the radiant heat of the forge's mass - not flame.
To bring something that size up to forging heat and then maintain it for hours at a time would be unrealistic.
It is VERY easy and inexpensive to build a small blown forced-air propane forge big enough to forge anything you want.