Yes, my stack temps are internal which is significantly more than external and no, my stack never gets red, guess it has something to do with stainless. I have played with it many times and no, I don't like blowing that much heat up the stack but I am getting a slightly better wood to syrup ratio with those stack temps than I ever did before and getting a much faster evap rate. If I back of stack temps, the boil slows down significantly. Every evaporator is different, what works good for me may not work good for the next person.

I would like to have a higher efficiency arch with most of the air over top of the fire and may endeavor on that sometime, but we'll see.