I'm late to this party. Sorry. I should link my flock, I have Comets, and also Hoover Hatchery "Rainbows" which are like somewhat larger Comets (NH Reds instead RI Reds in the genetic background, and something else). I eat a lot of older, primarily "egg-laying" so called dual purpose birds and try and let my more meaty birds have a chance to breed.
I have a "culling project".
The answer, on an older bird, is this. It's tough. Stew, stock, or sausage. Unless you are using the skin for something (like a sausage inclusion), its worthless. Don't bother. Save yourself the time and disrobe them, don't scald and pluck. That's going to affect your yield. If your butchering is good, you should get a carcass yield around 74% of live weight. So a 4# Bird should yeild about a 3# carcass. Remove the bones, you have about 70-75 of that weight. Remove the organs, 70-80% of that.
Don't like math (or haven't had coffee yet - I feel ya on the coffee thing).
Full Grown comets in my flock range from about 3.7# to maybe 4.4#. They yeild a carcass from 2.5# to just over 3# in weight. I keep the heart, liver gizzard, which leaves me about 1.7 to 2.25# in meat.