I have a new Rivendell which I will now become my main commuter but at times I'd like to still take my Specialized Tarmac to work. I've used the Tarmac for many years but the commute started to become more uncomfortable as I got older since I was also wearing a backpack with my change of clothes and other work related items. I purchased a Carradice tail bag for my Rivendall but was wondering if I could also connect one of the Bagman QR supports to the rails of the carbon seat stem so I can use the Carradice on that bike also. Has anyone ever used a Bagman on a carbon stem and do you see any issues with having it attached since it only connects to the aluminum seat rails?

I think the carbon stuff is incompatible ... steel saddle rails, aluminum seat posts are safer picks.

I have several Bagman racks and wouldn't clamp one to a carbon railed saddle. You have to tighten the clamp pretty hard to keep it from loosening and that could damage carbon rails.