Ah, this perfectly explains the crappy (non-desired) behavior I had with my 1st attempt with the small rotor. I was sending it close to 900mB/t of steam and it could only handle 625mB/t max.
On my 2nd rotor, I chose a 16,000L/s, or 800mB/t 'optimal' rotor, which means 800*1.25 = 1,000mB/t max...