The FSA Wingpro bars I use are aluminum and are ovalized at the tops. I find this to be more comfortable than a round bar. I don't feel a need to use carbon bars but would not hesitate to use them. Measurements on these bars are a little tricky since they flare out at the ends. So they are wider at the ends than where the shift levers are mounted.
Normally I use a 40cm bar but for these I use 42cm. Some bars are measured C-C and some are measured outside to outside.