I do not have a Calfee with S&S couplers but have had 2 mountain bikes with them and can say that they never gave me any issues and you could not tell that they were there. Much better option than a Bike Friday (or similar) in my opinion. My only reservations about them was using them on a high end bike period. I never liked the idea of putting a $5k - $8k bike in the hands of the airlines or UPS period. So I have a good but not great (Salsa) mountain bike I use when I travel. If it gets damaged, lost or stolen it is not a crisis.