I've been messing around with it on CM currently, my build don't seem to have the option under performance to turn on transparent navbar and status bar.
I've managed to enable it by changing the boolean in frameworks/base/core/java/android/app/ActivityManager.java from 'false' to 'true'
in the commit here: http://review.cyanogenmod.org/#/c/57471/
it implies there should be a check box to enable it.... but there isn't?!
I've checked my code against the commits and it is in my code, it has merged, as stated by the commit status. so unsure as to why it isn't coming up...
Odd that it's in the code and in the build but not enabled on the front end. Think it is enabled with the same logic that "Device Parts" used to be, such as the Xoom's charging light option on 10.2? Where that setting is only activated if your device is on list X or list Y? I haven't run my own build before so I'm not 100% sure either; maybe there's another commit needed to actually enable it?
Either way, glad to see you got it working on your build, I'm going to try this out today since I'm still running stable 10.2 on my Xoom (didn't want to do the bigPart repartitioning).