Dipstick tube in the freezer?? Anyone done this?

Sure i'll give my 2 cents here............
I would grind/polish the tube until it's a tap in type of press fit and use some RTV sealer on it.
You will thank yourself later if you ever have to remove it again!
It wouldn't take a lot of time really, it's only an inch or less that you're dealing with and it's a 1/4'' or so o.d. tube, you could even do it with a coarse file in 10 min or so from where you're at now..........