winemana 40% Black Shade Cloth, 10 x 20 FT Durable Mesh Tarp with Grommets, Resistant Garden Sun Shade Netting, Shading Antifreezing for Pergola, Greenhouse, Plants Growing, Chicken Coop

When you refer to your "shade sail" I cannot help but wonder if is somthing that blocks all the light, like a canvas awning. Wanted to mention that here in Texas I mainly use 35% or 40% shade cloth. It is looslely woven and blocks only part of the light (in this case 35% or 40%.) It lets enough through to maintain plant health while stopping the excess that can be damaging. It comes in a range of light ratings. If you already know all this, please excuse my comment. When I was new, it wass the kind of thing I didn't consider. This is an example of what I use. Not promoting the brand. Just an example. It comes in many sizes. Shade cloth link