I was teaching in VA today, and got to meet another of Strafe's half-brothers. (He has a lot of those, but most are in Europe)
You should be able to immediately tell which one is Strafe. The other pup looks a lot more like Fetch. He's not quite 6 months old, and is clearly in a bit of an awkward stage. And despite the way the photos look, the other pup, Biz, is not quite as big as Strafe yet. I am guessing he will finish up larger than Strafe though. Strafe has been holding around the 20.25 to 20.5" mark for a while now (about 52cm). And he may put in a late growth spurt, but he seems like he's mostly done. He was always the smallest boy in his litter, and as long as he can confidently jump the 26"/65cm height, I'm Ok with his current size. He's very athletic and coordinated and always has been.
Biz is from the Sky x Fetch breeding, and lives in Virginia.