Also, I get a different number. To clear 5.80 with a 4.83m grip, it is a 1.17m push, I think you calc'd for a 6m (1.37m)? No big deal. 1.17 is the top of spectrum, but has been done before, 1.37 as you mention is near impossible, or rather at that point you should be gripping higher.
Joe Dial pushed off 53" on a regular basis. But he was definitely not a double leg swinger.