I use Dutch's tarp pull outs and love them. Easy to clip on, can place them where I want them (depending on which hammock I am using) and can move them to another tarp if I need to.
I bought 2 pair and have used them on my 12x12 winter tarp when it was really windy, but usually use a single pair on my small tarp.
"Bye bye, boys!"
"Have fun storming the castle!"