I do have problem with power balance left and right side using my crankset for a few months now. I have tarmac SL4 and have 2016 S-works carbon crank arms installed correctly and drive side arm is futher 5mm. Do anyone heave this problem those crank arms are asymmetrical or it should be symmetrical. This is a big problem for me because after few hours on the bike i have back pain and cant find my place on the saddle. Ive been on bike fitting and bike fitter said to me that i have my drive side crank arm further for about 5mm.