Welcome to the Maple Trader Coatesy. You are doing OK with 3 bottles of liquid gold already. As Jeff said evaporators do not have a top, the pans set on a gasket and the pan bottom is the top to keep the exhaust gases where they belong. You are correct, remove that layer of tin and you will get far more heat to the pan. Is the barrel stove part insulated? If not you will gain a lot more heat to the pan if you put a layer of fire brick from the grate up.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.