But there's a way I think to pull the sides out all the way across the face of the tarp, and also permit the lower portion of the tarp wall to descend more steeply to the ground, and so give more protection from the side.
How about taking a lightweight replacement tent pole and run it the length of the tarp wall, attached at the sides where HC4U would put the extra tie-outs. Attach side tie-out lines to that , and as you pull on the ends the pole will bring the side out too.
Not straight unfortunately, unless you have really stiff poles. But who knows? It will be fun to try and see what happens.