I know this may sound odd, but I found a alternate to pinning grosgrain on my tarp project. I broke out the good old military grade stapler.

Since it takes me forever to finish a project, staples allowed me to ball up the tarp and throw it into my sewing trunk (am I allowed to say that) without worrying the pins my poke the fabric.

Plus with a 2 year old always at my side (love it) I don't have to worry about boo-boo's from the pins.