I published a post introducing you to Jon's blog a few weeks ago. I mentioned that there were some real quality posts on his blog, and I meant it! So much so, that I felt it necessary to re-post one of Jon's tutorials on a topic that comes up often: custom curtainwall mullions. Yes, that's right, you CAN create custom profiles for your mullions... You aren't just stuck with the OOTB profiles...
Custom Profiles
Posted by Jon McFarland on Februrary 25, 2013
The template consists of two reference lines; the vertical ref line represents the center of the mullion while the horizontal ref line represents the face of the curtain wall. Everything above the horizontal line will be behind the face of the CW and everything below will be in front to the CW.