Im working on a cat cut tarp (my first one, hence the question) --how deep do you make the cat cuts? do they all need to be the same length? Also, since Im planning on trimming the cat cuts with grosgain , do I just cut the arc with a rotery cutter and then sew on the grosgain? (verses useing a hot knife to seal the edges----since the grosgain is going over the top anyway, do the edges need to be sealed?) Thanks for all the help!