NEED TO KNOW LENGTH & WIDTH OF BOARD BEHIND SEAT BACKREST ON 5WND & DOES IT ATTACH TO PACKAGE TRAY OR TO THE BODY OR BOTH & HOW & I BELIEVE IT IS SUPPOSE TO HAVE A FEW LARGE HOLES IN IT WHAT SIZE ? & DOES IT HAVE AN ARCH LIKE SEAT BACK OR NOT ?---ANY HELP WOULD BE APPRECIATED--- I Have the orig pkg tray