I have plugged holes with small metal patches with closed cell foam gasket on the outside patch against cab and a second patch or shape inside that bolts or screws the two together through the hole
This allows for ready removal if I want to modify it to run a wire or hose later and also doesn’t change the cab metal from stock
A double sided metal patch is stronger against debris and fire
And the gasket keeps it dust and water tight
This method is likely overkill for small holes and your time might be worth more than mine
-s
