I would examine that tarp closely.
Make sure it's opaque.
I heard that northern or harbor freight had a good tarp, but it wasn't cheap cheap, just a good deal apparently, but very heavy duty.
I think I found it for $80 up.
I haven't found anything that is really better than the shelter systems tarps consistently.
I checked out a sample of it.
Even the good chinese tarps cost more.
Opaque requires a black or metallic layer in the middle or great thickness.
Even my very heavy billboard tarps aren't opaque with one layer, and yes it matters.
Black billboard material is more likely to be opaque.
http://shelsys.com/