Chuck - what kind of kettle are you working with?
For my SS Performer, I removed one of the bolts holding the gas assist and routed probes through there:
For my WSM(s), I always remove one of the support bracket bolts and use some hardware (plumbing isle at Ace) along with a lock collar:
I have not cracked the code on a regular OTS/OTG, but as long as the kettle is not vintage, would have no problem drilling a hole right below the charcoal grate for a grommet. I would use the same hardware as I have on the WSM above.
Good luck,
Winz