BACKGROUND: Decided to extend an already existing opening in this non-load bearing wall. With all the electrical and plumbing it's just not worth removing completely. Besides, wife likes the idea of having a family computer desk in the corner, etc.
QUESTION: What is the best way to stabilize this half-wall? I still need to frame out the opening and I'm guessing the drywall will add some rigidity, but I want to make this thing is pretty much rock solid before finishing. Currently it wobbles a little if I shake it hard enough.
(The partial horizontal 2x4s you see in the picture are just temporary supports I put in for cutting out studs and drywall)