My rig came from the factory with one, it's mounted in the closet, right on top of the box for the electrical cable rewind over the engine. Nice hot spot in case of an engine fire. Doubtful anything in it will survive a fire. No room under the bed due to the OTR bedroom air con and slide mechanism.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 Jeep JKU Dragon Edition