Hello; I try to use vibration absorbing engine mounts in all applications mainly to protect the airframe and radio gear. I would make sure that there isn't something loose. Properly mounted, a 4-stroke doesn't vibrate enough to notice. I do have an OS 48 surpass in a midwest Suhkoi that is ridgidly mounted that works quite well. I have to keep an eye on the mounts attachment to the firewall, they loosened for the first 4 or 5 flights, but have settled down now. I bought quality allen headed screws and tightened them down well and haven't had any problems since.

It will smooth out a bit as the hours pile up.