The pic is a Dr. Who heifer that I have for sale over in the classifieds. My experience with Dr. Who is that they'll be fairly sound, but I did have one get a little straight fronted this year on a cow that has had sound ones by Heatseeker, Cheap Trick, and Angus sires. He sold OK and will work, just not totally faultless on his front legs/shoulder angle. I haven't had a bunch of em, but I'd say he won't downsize any, if anything maybe adding a slight bit of frame at our place.
Have only had a handful of Carnacs. Sizewise, my thinking is that they will pretty closely follow the cow. Probably bigger framed more consistently than Heatwave at my place. As far as soudness, he has a pretty bad rep, but ours haven't been any different than the Heatwaves or his other sons. Some are sound, some aren't, on a variety of cows. IMO, thats just the way it goes when you breed for those extremes. Just watch the genetic defects (TH especially here) and hope for the best