Well, VS Legend, even leaving that little bit of space at the top, the shims still create a great deal of strength in that area. There's less area susceptible to flex, which is what causes that crack to form in the first place. While you are correct that shimming to the top is stronger, having that small place for the HG to bite into is probably the lesser of two evils. It'll be less likely to blow the gasket under very high cylinder pressures.