[Arcturius]

Or if you're really worried about the board flexing, put a thin piece of neoprene or closed cell foam under the socket, and a piece of 1/8" alum. under that so the bolts can pass through it.

Even better, drill and tap the backing plate, and put 6-32 threaded rod into it with some loctite, so you have the bolts always hanging out the front of the mobo, but connected to a stiff backing plate. It'll put only compression on the mobo, and no twist. Plus, all the bolts will always be lined up perfectly. If you really didn't want the thing to shift, you could even stick the insulation and the plate to the mobo with some goop or something.

You're keeping your chip cool enough that you don't care about the small amount of cooling ability that you'd lose by insulating the back of the mobo, right?