So today, I drilled a hole through the wheel well of my RV, so that I could run a propane hose from an outside tank into my rig, and connect it to a portable heater. The wheel well is aluminum. I lined the hole with a rubber grommet. I considered @MightyBigCar 's advice to just open a window screen slightly to let the hose out, but doing this use up a lot of hose length in going up the window and down the other side. The set up I did here gives more use of hose length.
https://octodon.social/media/MOlBZTjowQWru4N3yLA