Instead of drilling through the drain hole I used the pre-punched hole in the center just above the drain outlet (White circle below the screw).
Easy drill just foam insulation and the interior plastic shell. Hand pushed an awl through it first to mark the location in the plastic.
Then drilled from the inside out. Sensor and wire fits perfectly!
I used a 7mm cap nut/teflon tape/o-ring on the exterior threaded drain tube.
For the inside, I ordered a rubber stopper. I used the stopper instead of caulk in case I ever sell the unit, it can go as a humidor or wine cooler.
I had to order 25 stoppers (min order) so if anyone would like one (No charge) PM me with your Addy!
Rubber plug in drain hole.