Hi Evan, I think the larger loaf will take a bit longer to bake. When baking in a 13-inch pullman pan, I would estimate the baking time to be about 25 minutes with the lid on, and about 15-20 minutes with it off, but keep an eye on the bread towards the end of the bake and look for an internal baking temperature of at least 190F. 

Barb

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