Yep that is how to do it.I've contemplated putting up some 6x6 posts and stretching out a big shade cloth. The posts could also be used for catfish skinning.
quality shade cloth has very strong edges and heavy duty grommets
I used work for a company that had a nursery and I grabbed a couple of them when the business went bust...I use them each summer and they have lasted like 4 -5 years so far...probably like a hundred bucks or so for a big one