Nyrod is nylon pushrod. I also use them for cowl screw anchors. If you drill a 1/8" dia hole into balsa or ply, that will be a snug fit for the nyrod, and the friction is probably all you need. However, if you want to secure them more tightly, a drop of thin CA will stick them in pretty tight. I insert the nyrod so just a bit--maybe 1/32"--sticks up from the surface; that way you can drop the CA at the outside junction and not foul the inside diameter.

Nyrod inside diameter is perfect size for the aluminum socket head servo screws from Microfasteners, which are much easier to turn with a hexdriver. Allen head screws for servo installation, cowl attachment, etc. are just no good by comparison. Metal threads biting into the plastic do not vibrate out and don't chew up the wood.

I have tried the servo grommets, and for some reason they disintegrated after not too many flights. I reinforce the cowl around the screwholes, first by CAing a CA hinge on the inside surface where each hole goes. I then epoxy a patch of 2 oz. fiberglass over the CA hinge. Then I enlarge the holes in the cowl to 9/64", so the protruding nyrod nestles inside the hole in the cowl. I've found this method the best I've tried so far--no rattling, no enlargement of the holes.