Starting last year I had three good Sizzles, fifth generation. All were Sizzles, normally frizzled. I bred them, I got about 40% straight, 40% Frizzle, and 20% curly/frazzle. The Frazzles did fine, yeah they had sort of brittle feathers but were otherwise normalish birds. Unfortunately predators got to four of my birds this year, including the frazzles and two sizzles. Such is life.
Which is a pity because I'd hoped to use the small and nearly perfect splash one in the future with some silkies I brought in. Having done it out of necessity I'd do it again. Frazzles are not always all that unthrifty apparently. These were outdoors, with a heated coop, but free range, at 8 weeks just like everyone else and still made it. I'm not a "rules'' person. All this "oh my don't do it'' means I go ahead and do it and see for myself.
I find often that it works out anyway. Sure, I might have to cull an unthrifty bird, but I have to do that with the other breeds anyway, it's not a lot different. And as was noted, a Frazzle/curly is a useful beast since all it's progeny will be frizzled even if mated to a straight feathered bird. That's a fast track that's useful. I got a lot of straights in this bunch, nice splashes , would have been nice to have a Frazzle to breed to them. Oddly they're all splash, none of the blues or blacks are straight feathered. Genetics are funny things. But I'm looking forward to what the seventh generation brings.