Summer shade for our T@B 400

We bought a new 400 Boondock last November and have an indoor storage facility for the winter.  We will keep it near our home in the Lake Tahoe area for the summer and fall.  The place we are storing it now has direct mid-day and late afternoon sun.  I am concerned the intense sun will prematurely “age” our trailer.

I am considering buying a breathable (that is how it is advertised) cover but wonder if it will make the trailer even hotter inside.  Are there any covers available that just go over the top and are secured to the handles on each corner?  That is really all I need.  If not, what do you more experienced owners think of the idea of a shade sail-type cover?  I can get something like that semi-custom online.  I realize that with any cover I will need to protect the windows.

Thanks for any advice you can offer!