IT IS ALL PREFERANCE BETWEEN THE 40 AND THE 20. MY UPHOLSTERY GUY SAID IT ISN'T THAT HARD TO INSTALL AND IF YOU DO HAVE TO BUTT IT UP IT HIDES THE SEAM BETTER. BUT I HAVE USED 20 IN ALL THE BOATS I HAVE DONE. AND ALSO HOW MANY YARDS DO YOU NEED, ARE YOU GOING ALL THE WAY UP TO THE NOSE?