I think either one would work depending on which stem length will provide clearance for your knees (i.e. will your knees hit the pads with a 100 stem?). with either one, you should still be able to maintain your current cockpit geometry just by adjusting the extensions and elbow pad height (the carbon x pads are notoriously high unless you know how to modify them so factor that into the equation). with everything else maintained, the 100 would probably mean the pads will be closer to your elbows, the 120 further down your forearm. your choice as to comfort.

with regards to aero, if you just swap out the bars but your position remains the same, then your body angles remain the same, so no aero difference. for the stem to have any impact, lower it to lower your back. if this causes your hip angle to become too acute, steepen your seat angle.

good luck!

Kim

That is the problem with the Carbon X. I loved mine but I couldn't get a good fit. I much prefer the newer designs with a seperate stem. The fit is more adjustable, so you are more likely to get it right.

Good luck.

After thinking about it I think I will get the 100mm - the saber has a really long top tube and my back is pretty good in my current position - my elbows are pretty far from my knees and to go any further forward would make pedaling uncomfortable. I have an M2 power racer that could push me forward but that would destroy the elegant simplicity of my current set up plus it likes to slide around while your riding. Also with the saddle pushed all the way forward I am alrready at 78% - I dont think I've heard of anyone going steeper than that...