Yup as he said!

You can even use bits of fuel tubing.

I cut a hole in the cowl slightly larger than the tubing. ( Thank's to RCKen for this trick! )...

I then CA the area around the hole to prevent it from cracking.

Then cut a very small piece of tubing, and put this on the screw. Preferably a screw with a big head, or a screw with a washer next to the head.

The screw with the tubing is inserted through the hole and bites directly into the wood, or whatever you are anchoring the cowl onto.

The tubing will expand as the screw bottoms out forming a rather nice anti-vibration mount.

Do this with four screws or more on the cowl.

Works great. When you remove the screws to access the cowl the tubing keeps the washers from falling out too.