As I suspected, the shrinkage was least in the plainweave shawl. When the threads have less room to move, they have less chance to shrink. Otherwise, because the boucle was used as weft, and the nylon strand around which the wool strand looped wasn't very shrinky, the structure didn't have much effect on the shrinkage rate. The warp yarns are all worsted spun, and less apt to shrink than woolen spun; plus many of them are treated to resist shrinkage.
In general, I like the versions woven in broken twill and a crepe with shorter floats best, so that's probably what I'll use in the upcoming boucle pieces. I have a teal green yarn, and a rust red yarn from the same supplier (Textura Trading, no longer in business). The yarn was originally spun by Baruffa, one of the top Italian mills. There are cones of coordinating plain 2-ply yarn in the stash to use as warp for both boucles.
Even after finishing, the cloth is very open and sheer. The boucle causes lots of distortion in the cloth, an effect I like. As I recall, each shawl weighs just under 6 ounces.
Be sure to click the thumbnail to see the larger image.