I use the same Mount.
Vibrations on Idle is normal and on four-strokes motor you get more vibrations then 2 strokes as you have 1 ignition state very 2 revolutions not like 2 strokes where 1 ignition state every revolution. As long as the Motor is well attached to the mount and the mount is well attached to the firewall....
go fly, enjoy and always come back from the field with less fuel and same number of airplanes. (Not opposite)
Regards
Amram
F3A Israel