Wow, just looked them up.looks like a great, sustainable meat bird prospect. I'll be very interested in seeing how they do for you.
I'm thinking about raising white laced Cornish and improving on their meaty qualities. It always seems that part of our problem with heritage breeds is that we've made them dual purpose, instead of making them specialized. I'd like to have a meat line, maybe the WLC or, even something like your Sulmtalers, Dorkings, or another large breed, selected for meat qualities, and, a nice, light, good egg laying breed that's easy on the feed bill and can take basically care of it's self by foraging. I love the silver leghorn. It's a small bird that eats very little, lays a lot of nice sized eggs, has a "camoflaged" color pattern, and is a great forager.
It seems silly to me to try to have one breed of chicken that does both. They will never do either well. By having dual purpose, you have a breed that eats to much and doesn't lay enough to justify the feed bill but doesn't weigh enough or gain fast enough to make a good meat bird.
Just something I've been thinking about, anyway. I've had a lot of birds of various species for over twenty years, usually on large, pasture situations. The lighter colored, fancy looking birds don't survive long in those environments. So, feather color is also a consideration for me. I'm trying to do a lot of research now, since we plan to move in less than two years and I'd like to have an idea of what type of sustainable meat birds I'd like to raise. I'm planning on some turkeys, too. For now, I'll just keep raising the Cornish cross as they make the most economic sense.