I already tried the registry settings and changing

BorderWidth to -1

PaddedBorderWidth to -1

However,  the title bars in W8 are still almost 50% bigger than W7.

That is mainly because of the advanced appearance which is not supported

in W8 anymore.

This means that working with a lot of open windows leaves less effective

modeling/drawing areas.

Does anybody know how to further decrease the size of the title bar?

I already have the title bar text very small.

The problem is that the title bar height is still twice as big as the title bar

text which is far too big. In W7 you can adjust it any way you like.