You said large morrors but did not mention the length of the stem.  If it is a long stemmed mirror and the stem is a narrow piece then that will definitely cause vibration issues.  A large mirror on a short stem will work better.  The larger the stem the more solid the mount.
But there is another issue, the type and length of your risers and also the length of your bars, and also whether your bars are hollow or filled with BB’s or lead.  A “filed” bar will do much better for vibration.

Spending more dollars on quality mirrors can make a big difference too.