Finding top edge of J hook (x=600 to 850):
x=640: top of J hook at y=915 (v=168)
x=670: top of J hook at y=913 (v=72)
x=700: top of J hook at y=908 (v=133)
x=730: top of J hook at y=897 (v=52)
x=760: top of J hook at y=881 (v=119)
x=790: top of J hook at y=857 (v=129)
x=820: top of J hook at y=814 (v=60)