Planing heads for increase in compression...

[StockMan]

Does anyone know planing a set of heads (and the intake accordingly) affects compression ratio?  For example, I have a 383 2bbl that has a stock 9.2:1 ratio, what would this ratio be after taking 30 thou from the surface of the heads, using the same head gasket? 

Also, how far can one go with this before making the parts unreliable (eg. head more prone to warpage), or, before it becomes impossible to match up the intake to the heads/block?

Thanks