The old-fashioned way of getting more heat out of a woodstove is to have a longer run of galvanized flue before it goes unto the brick chimney. I had one that included a bifurcated flue: a section of straight pipe, a tee, 4 elbows, another tee and straight pipe to the flue collar of the masonry chimney. Admittedly, a cob job, an eyesore, and a creosote distillery, but that creosote made dynamite kindling. This is the adirondack approach to wood-fired efficiency.