I have a portable tank that goes under my sink cab.  Took the under van tank right off.  I hold the tank inside the cabinet with a snap buckle webbing strap and have drilled a few vent holes into the floor of that particular cabinet and sealed it off.  Now, before all you "Belts AND Suspenders (just in case)" guys tell me about blown up vans and how unsafe I am...Don't bother.  Yah, it may be slightly less safe than having the standard tank hanging down under the van, but I think it is actually safer.
  And, my fridge runs full time for about 6 weeks on one filling.  I don't have to maneuver the whole van to within reach of some grumpy propane dispenser..   In Mexico, that is often impossible anyhow because they often don't have the right fittings or whatever.  When on an extended camping trip, I take along an extra tank (they fit  into a plastic milk crate just dandy to keep them from rolling around) and have a full backup for the times when I am hours(or days) away from a propane source.
  I've seen vans (more than once) with the propane tank half ripped off and dangling on the road, kicking up sparks as it is dragged along...That can't be too safe, right? 
  Don Hanson