Check this out (air race survival on this site) http://www.equipped.org/simon_t.htm

This guy has to fly over mountains, bodies of water, and deserts throughout his flight, so it's pretty similar. Doug does a really good job packing things down to something small enough to fit into a seat.

I agree you should make use of your aircraft's ballistic parachute if you ever go down. The parachute and shroud lines are your friend in the mountains or deserts. As mentioned, refer to USAF survival manuals to learn how to make use of them.

As far a seperate shelter is concerned, you probably don't need one (with the exception of an emergency water landing). You have your parachute, and you also have the cabin of your aircraft, which is better than any tent assuming it's intact and safe to stay (not burning, etc).