I run a Smoky Lake 2X5 Corsair with a 2X4 flat pan (about $2250) and can run 12 GPH all day long. I welded a 1X2 filler plate to cover the void for small batches, and bought a 1X2X20" preheater pan for the big batches. With the preheater (I think $200 more) i am running 16 GPH with the 2X4 flat pan.