I go by the rule of thumb that a 3/8" line is good for 400 hp. Therefore, individual 3/8" (-6) line from the tank to each pump, the same to where they meet, and 1/2" (-10) to the regulator, and you can go -6 to each carb if you're running two, or best to stick with -10 if you're only runing one carb.
In other words, yeah, like he said.
JHMO,
Dan