To, me the simplest way to determine a single hammer max, is what can you average on a barrel board, single hammer.
Given say a modest (110K single hammer start, 7800 conveyor avg, 5500 elevator avg, 8000 rivet avg)
Barrel average (10,500) = 1,000,000
Barrel average (11,500) = 1.06M
Barrel average (12,000) = 1.08M
Barrel average (12,300) = 1.1M
Now, if you think you can average 12,300 with single hammer, that's pretty tough.