I read several places where grommets are installed in existing bolt holes to introduce probe wire(s) into the smoker, lamp hardware installed in an additionally drilled hole(s), water sealed electrical grommets also installed in an additionally drilled hole(s), and silicon grommets to line additionally drilled holes, etc.
I do not think the hole(s) would corrode because smoke residue would eventually build up to protect the exposed metal, so I am not exactly sure what the grommets are for except to fill the hole and maybe reduce sharp edges. And I am unsure if the probes ends would fit thru the holes. Not to mention some of these holes I've read about and seen on various sites are fairly large diameter in order the get the probe ends to fit thru them.
Therefore, I decided that I would simply cut a small slit in the lip of the center section with the dremel to allow the probe wires to simply slide into the gap. The wires fit under the lid with a very small opening so I don't have to worry whether the probe ends will fit thru the hole(s) or not.