I've never heard of this either but I'd have to say Chardonnay/Puppy would be in the category of "bird-bones". She's a long lanky thing and only weighs 10lbs. However, she's smaller than most of the cavalier's I've seen, though my friend who also owns cavaliers says that the european cavalier's are smaller than the american (that's probably because ours are just a tad bit plumper).
She does crazy tricks and things like you described and she runs ridiculously fast for a small dog. She also gets hurt really easily. I remember when she got her yearly vaccinations, she was sore for about a week and there have also been times where she's been in the way and accidently gotten hurt. She's way for fragile than our other 3 dogs (I live in an appt with two other roommates). She's more fragile than Titus but he's a big baby. And my roommate has a chihuahua/Jack russel mix that actually weighs more than Puppy.
My babes: Chardonnay B/T Female(or "Puppy" Spring 2007); RCF's Vin du noir et blanc TRI Male(or "Titus" March 18, 2009)