(solved) -- LP cyls on a hitch rack

I am looking to buy a hitch mounted cargo rack with high sides, then bolt (using Loctite Red) onto it a propane rack, and a padlock for the handle, so it doesn't work loose. This would be useful for storing an extra pair of 20 pound propane cylinders on the back of a trailer, or a motorhome.

The bottles will be well anchored, but my biggest worry about rear-enders. Would I be going too far into Ford Pinto territory with this setup, especially behind a motorhome?

Edited -- bad idea, confirmed... won't happen.