Josh - Only boiled 100 gals with the damper. Pretty difficult to prove anything in this business because of all the variables. But it appears that after closing the damper with the blower going, the front pan boils harder. Will it save wood or improve the syrup to wood ratio.....I do recall Nearing, a raging capitalist despite his profession, writing back in the 1940's of installing dampers on both his natural draft 5X15's (had 2 identical setups but only used one at a time in case of catastrophic fire) claiming they saved wood. No question the stacks are over sized after the units a retrofited with forced draft. And the floats/float boxes also are also not designed to cope with the higher evaporation rate of forced draft; a real challenge to maintain a gradient. Still completely tore between a bigger unit and an RO. Keep up the good work. Bruce