What about weather striping adhesive, like what the trunk seals are held in with?
That stuff is too soft. The rubber grommets do have a lip to lock them in like the factory hole plugs, it just that they shrunk over the years and get smaller than the hole. I heard there are some newer power window kits for our cars. PThey probably will use smaller holes and fresh flexible wire. No reason to have holes that big unless you're working with the old factory stuff.
