I don't know the right answer but I would think less than half the weight, when you consider they are boneless and the dark will have the bone in unless its a preformed roll yuk. But if you are not serving any dark meant don't invite me, I want the dark meant thank you. If you are only feeding female types then you may use more breast meat But at the end of the day in my house with 6 o 7 ladies and 3 or 4 male types at the thanksgiving table there wont be much dark left.
I mite add figure about 1/2 lb per person then add a couple more people to that equation and buy that poundage if breast meant. I know that is not a proven formula. Hopefully you will have leftovers cant beat leftovers.
When the going gets tough, I take more fiber.