I really think that the key to reducing vibration is to get the engine timing as accurate as possible. And when you replace the rubber mounts, there is a break in and adjustment period when you tighten and loosen the bolts till you get it just right.
Vinyl door edge for back edge of Quietline hood McMaster Carr # 8451A47
Hood hinge tighten up;
https://www.onlycubcadets.net/forum/...61&postcount=7
Sometimes the spring that holds the side panels together will rattle against the muffler box, some put a length of rubber fuel line over it.
I have heard of people using wood stove gasket rope between the muffler box parts, never tried it.
How about your driveline? If the ball bushings, driveshaft ends and rag joints are worn out that will vibrate too.