That all helps quite a bit. The plastic that lines the top of my freezer is curved for whatever reason. I'm likely to have to cut that out and add a layer of the pink insulation sheathing, then put plywood on both the outside and the inside to allow for a solid connection between the top and the inside.
Hadn't considered T-nuts. I was just thinking carriage bolts on the top and regular nuts on the inside.
Ok, knowing that I'm going to incorporate a drip tray I'll want to build the space for it to recess into the coffin box rather than just cutting a section from the lid of the freezer. Just typing it out I realize cutting the lid like that is a bad idea...
I really liked that Idea and am planning to modify it by T-ing off the connection at the top and using a pair of 4" PC fans to suck the cold air up from the bottom and push it up top. I was going to power them with a rigged ATX power supply on the outside and just run the wires in via small conduit with the temp control sensor. Does that sound reasonable? Is there a flaw I don't see? Is there a better cheap fan/power supply solution?
OK, MAIN QUESTION:
Where is the safest place/what is the safest way to run the temp control sensor into the freezer without damaging the integrity of the freezer?