I have a 2x6 raised flue grimm evaporator. I want to get as much boil out of it as possible but also plan to upgrade to a larger evaporator in a few years. Would building a airtight door help much on the grimm front? Its also up on blocks so this would have to be sealed also I would assume to get effects of airtight door. I have under fire air now but still get a ton of ash. Last year redid arch with ceramic blanket it boils harder but think I still can get more out of it. If I build a preheater want a seperate unit that steam comes off of hood then enters. Not sure what size pipe I would want to use in this. Thought of using 3/4" copper to enter and exit preheater then go to 1/2" copper inside and split it into 2 seperate lines. Would 2 1/2" lines flow 100 gals per hour on gravity feed? Any ideas on all of this?