Tony, your fabricator is wrong. Back when I first started I had 27 taps on a 4 section 2x3 pan, it worked very well, that year I made a judgement error and after each early season sap flow I added more taps until I had 70, that 2x3 ran 72 hrs non stop and after the 72 hrs I had more sap left than the first night when I decided between my wife and me we had to boil around the clock. On your 2x4 just don't grow too big too fast.
On mine it had 4 sections and I drew off very slowly as it reached 219F and then finished it off inside which did,'t take very long.
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.