Sitting under a tree around noon in tropical heat, one realizes that partial shade is also partial sun -- and that the difference between partial sun and zero sun is very real.
Most tarps and tent flies only block some of the radiation.
Are there lightweight materials that block 100% of the sun's rays?
Are there coatings that can be applied to existing tarps and flies?
[It seems to me that Jack Stephenson wrote something about this somewhere -- one of his tent options might have been aluminized coatings that gave something close to 100% shade....]