A little nervous!

I would look for a 4* shim and try it. It would put you at -5 which is a decent starting point. If it still vibrates roll it up with a 6* shim. See if the vibration is better with the 4* shim. If so, you are headed the right direction, BUT, rolling it up too far will inhibit the hook potential... It's a balancing act to some degree.