It's actually the same "speculation" that industry insiders are using...nothing "piss poor" about it. Spring Hill is the only one that kinda surprises me, although this is not the first place I've heard this. Spring Hill is new and large, but it's not close to GM's core plants and that hurts.
Flint builds the big GMT800s, like you pointed out. THAT is why it's not on the block. Hamtramck, when up to speed with the Lucerne, should run near capacity. And Wilmington...poor, Wilmington; if the additional models due for that plant work out, Wilmington could be producing 150,000 (perhaps even 200,000) units in the next few years.