Go to WindowFX5 config editor. Open the "animation" tab and then click in the bottom left on "movement". On the new page, you will be able to activate the flip option. It is the first on this page.
When active, just click with the middle mouse button on a window title to flip it. To unflip, just click anywhere in the window with any mouse button.
This of course only works when "Make a middle button click on the titlebar minimize the window" is deactivated (can be found at the "window management" tab").