03'Silverado2500HD

it's a power mirror and there really isn't any slack in the pivot.

I recently installed some aftermarket Tor mirrors on an 03 and the glass vibrates/shakes when driving on normal roads and on the highway. I was thinking about putting some left over Sound deadening on the back of the glass, as a way to mass load them to slow the shaking. I don't really mind the shaking too much but if I already have something that will help with it, it's worth a shot!? What are your thought about this?