I've read it only takes .3-.5 psi to break a house window. I'm not sure how much protection plywood's going to offer against the shockwave, but it's going to offer some protection against shrapnel that used to be your nutball neighbor's house.
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Hope for the best and prepare for the worst.

The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane