[elhigh]

I wouldn't take adding a tail completely off the list of possibilities.

Adding a tail about 10-15" long would put it almost exactly the same length as my truck. Your wheelbase is a bit shorter and your width is very similar, and parking the truck is a snap even in crowded conditions. Your experience even with a modestly lengthened Prius should be similar. The gains wouldn't be as impressive as a full-on boattail, but not nothing either.

Freebeard's suggestion of PlastiDip on the roof and hood are pretty good ones in my opinion. Provide most of the cooling you're looking for, protect the original paint and completely reversible. Win-win-win.