Checking in with an update...
At 8 weeks I slaughtered the 8 largest (as best I could tell) out of my 51, but they were only about 2lbs each, dressed.
I slaughtered three more of the largest ones at 10 weeks and got ~3lbs each. I hope to catch the rest of them at 11-11.5 weeks and average 3lbs each. They have only been eating 12lbs of feed/day (my recipe, fermented), so I don't think it will come out to be a poor conversion of feed to meat, just slow. I was afraid at 10 weeks they might be getting tough, but no! tenderest most flavorful meat yet! I was very happy with the quality.
I'm thinking that the slow gain has more to do with waiting for them to eat their peas before giving them more food than with my feed recipe... I'll learn more with the next batch in the spring! I may go back to jumbos.
~Rachel