I was able to mount my G4 onto my C3, I couldn't use the clamp mount but it came with an adhesive one too, I put it behind the sunvisor switch. I can take a picture tonight if anyone wants to see. I don't know what a Sena is like but I'd imagine they have to have an adhesive mount too.
+1 on the pro, I'm half tempted to try and sell my C3 to upgrade.