I really couldn't say. I've never noticed any shrinkage but then again I've never put on more than a "skim" coat (1/8" or less). Much like any filler, if you apply it too thickly, you'll get voids and bubbles. It's just the nature of the beast.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now