I've always read it's 1 GPH per square foot of flat pan.
What sort of rate did you get from the 5 pans.
I got around 5.5 GPH from 3 steam table pans.
If your arch kept all your pans at a good boil I guess you would max out the potential of a 3x5.
I'm new to this so there's probably better info to come from others, though this forum isn't as active as it was during the season.
2019-2023 40 to 50 taps to get 8 to 10 gallons of syrup
2018 Built the sugar shack, produced 10.5 gallons (converted some to sugar,& cream). taps varied 45 to 50
2017 Built 2x4 arch for a divided pan, 8.5 gallons from 30 taps increased to 42 taps during season.
2016 Produced 3 gallons & 1 quart Syrup, Block arch & 3 buffet pans, 12 taps
2015 Thought about tapping