I'm running single sivot brakes on one of my nicer road bikes. 105's from the early 1990's. They stop fine. The slight difference in mechanical advantage has two effects:
1. takes more hand pressure to lock up the wheel
2. the pads can sit a bit wider apart and thus give more space for an out-of-true wheel or for riding home if you break a spoke.
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"c" is not a unit that measures tire width