The best would probably be rolls of diamond mylar. Personally, I've been using just a very bright flat white paint andI can't imagine it being much better but being I came into a few rolls of mylar I may just hang them up next time and see how different things turn out...or not.The one i got from the home dumpo is a Styrofoam with a white side which has all the printing and the other side is a thin foil it my be Mylar, I don't know. Plants look good, my concern is could I do better with a different material>
bill