just draw out a scale pattern of what the design will be and determine if you need more. If I were doing it, I'd just make up a cut list for all of the tin pieces and have them cut. That would maybe run $10-20 more but on their shear they will all have nice unrippled edges and the sizes will be right, especially if they have an 8' shear. Most bigger shops do. (for a 2x4 arch the longest single piece will be somewhere around 5' long, figuring for the 4' pan or pan combination plus the base stack at the back.)
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.