This brings up another point. Even if I torque it on there really well,
what happens when the whole thing heats up in the furnace? Is the
bottom going to fall off?

Man, I am so stupid for not having thought of any of this before.

Bob May wrote:
Get a wrench to tighten the end cap. If you have a torch, you also will do
well to heat the endcap and quickly put it onto the nipple and that will
make things even more tight. Don't use teflon tape or any other thing like
that as the tape will evaporate the first time that the thing is used.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!