All you need to do is adjust the flame with the damper to account for the difference in the increased mass flow rate from both the colder air and the increased flow rate of the combustion air fan. It's true this is offset slightly by choking down the damper. Still, it's like putting on a extremely large air filter on your car vs a small dirty one (a smaller restriction vs a big restriction on the intake). The car will run more put out more power with the larger filter and even more with the colder air. In my opinion, once a good enough adjustment is made to the damper after the OAK is installed, that will probably be good enough irrespective of typical outside air temperature changes mainly because you've maximized the combustion air fan efficiency - you have maximized the flow to the burn pot.