Jim,

Not worried about wind in the least.  That cable is clipped in every few inches right along the inner corner between gunwhale and canoe.  There's nothing for the wind to grab.  As for vibration, transducers are designed to handle pretty rough conditions on a fishing boat which I have to think is harder on them than travelling cartopped.

At any rate, I've been rigged this way for a few years with no issues so hopefully that continues to be the case.