I don't neccessarily think it's the POUNDAGE of meat that matters, as much as it is the dimensions.
I always try to get a good measurement of the meat in the cryovac to see if it will fit in the cookers.
I have had some butts that were not as long as others that weighed more - but would fit in the cooker. Whereas other butts that were longer, but thinner, wouldn't fit (and they weighed less).
So, I guess I said all of that to say that it in my experience, it isn't so much how much they weigh as much as it is what their dimensions are.