Concrete cladding panels as curtain walls

[harrowboy]

hi everyone I have been trying out the new Revit 2010 for the past few days and found it reasonably straight forward except custom families..

 

I came across this tutorial abt making custom curtain panels,

http://autodesk-revit.blogspot.com/2008/09/concrete-cladding-panels-as-curtain.html

and encountered some problems, that I couldn't find an option to flip the panels as the author has done. I have assigned double-horizontal controls in my custom wall panel family but it doens't seem to be effective once I load it into a project. Any suggestions?