While your configuration will be different, I had a Grimm arch with at first Leader pans a 3x2 syrup pan and a 3x6 raised flue pan, with high pressure AOF and AUF it got 65 gph. I later sold those pans and bought a set of Thor pans. I made some changes. I ordered custom built pans, 3x3 syrup pan and 3x5 flue pan with 10" tall raised flues (flues were 7" tall in the old pan). I had both pans made 4" taller than normal.
I boiled 8-12% concentrate in both after my first 3 seasons on the original pans. I also had a pre-heater in the hood. My new pans got 72-76 gph and while the original pans made good syrup, I think the newer design made better flavored syrup, the pan ratios being the difference.
If you concentrate to over 12%, I suggest the flue pan to syrup pan ratio change. On high concentration most producers have a short flue pan and a long syrup pan. For example I heard of 30%+ concentrations going with a 7x4 flue pan and a 7x 14 syrup pan or similar ratios, in fact I think I've heard of over 30% concentrations having no flue pan, all syrup pan.
If you aren't going extremely high in concentration however you need a flue pan to attain the production you want.
Dave Klish, I recently bought 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.