I dont know about that advice about the 100lb cylinder. Sounds pretty risky to me. You would be sleeping right over and that compartment was not made for it.
Also I do not beleive that the extra insulation package and dual pane windows are all they are cracked up to be. I am sure that anybody who has them are going to say they are. As i said before I am a builder of new homes on Long Island. I am a Energystar builder & have been a draftsman trained in heat loss & Rescheck, which is calculations done on new homes for energy comparison to State codes. You lose 60% of your heat through the ceiling, most of the rest is lost from the floor, windows and radiant cold walls. The double pane windows as I understand them are just that , double pane. And its not only the glass that comes into play either, it is also the frame, is it tight, no air seepage and does it have a thermal brake? Not the same as an Andersen double pane insulated. All my homes have a minimum of an R30 in the ceilings & R22 in the walls. I thought I read some were that my Bighorn came with a R7 in the walls & a R23 in the ceiling. I certainly know you can never insulate them as much as your home. Don't let the salesman at the dealership lead you to beleive their insulation package will make you feel like your in Florida.
Considering all this I have had many trailers & motor homes, they are notourious for air seepage, cold window frames, cold walls & not being able to get enough insulation to make them efficent.