When you copy the texture into the middle window to create the alpha channel for the bump remember to INVERT it (the black&white button) or the bump will appear to go INWARD rather than OUTWARD and you'll have to use negative number values in the 'amount' to get the bump to look right. Why they did it this way is beyond me. It uses regular, non-inverted alpha channels for everything else, having to invert it for the bump is just clunky.