I've grown Cobra a couple times and they were all single cola, decent effect, and fruity smelling buds... not the biggest yield, though. (To be honest, my simple grow techniques do not bring out the best, yield-wise)
I'm also trying to work more toward a "single cola" pheno to get the most out of my situation. There are some very promising candidates among the Dragons, based on my first try with them. Bad Betty is another one of Wiz's that seems to be inclined toward a single cola structure. The one I grew was, and every one I've seen a pic of has been... very nice "up" effect on the Bad Betty... with a similar yield to that of the Cobra. I have a couple more I'm working on, as well... just for my own purposes.
If I trip over something that works for me, I'll give you a shout.