Weight said:
1. If the bottle vents while laying on it's side, bad news. 2. You can never have a pool of liquid propane. It evaporates into a gaseous state and a spark will be your end.
1. bottles should ONLY be used, carried and stored in the position(s) they are designed for. For ALL tanks designed for portable consumer use, that means upright at ALL times while in an enclosed area.
If the over-pressure relief valve intake / dip tube is submerged in liquid when it opens, HUGE volumes of expanding gas will result and catastrophe is VERY likely.
Forklift tanks are horizontal, the holder bracket keyed to a specific orientation for just that reason.
Other industrial designs can be stored either way, but in use are specified only one way or the other.
But unless a qualified gas tech signs off on the setup, messing around departing from mainstream standards is unsafe and likely illegal, and forget insurance covering anything.
2. Propane as a gas is heavier than air, tanks inside the living space should (IMO must) be carried in a box sealed up wrt that space.
If the mandatory bottom vent opening to outside gets blocked, the gas does indeed quickly pools from the bottom up.
If no proper box, a tight living space will have that pool fill from the floor up.
People can and do "drown" from the oxygen being floated up above their head while sleeping even if no ignition.
I take many crazy risks in many areas of my life, but propane is not one of them.
