rear end too light or just me?

[Paulfzs]

im about 11 stone, took the bike out for some fast paced roundabouts and straights near redline in 3rd for most of it with some mates, problem i found which almost put me into the lane divide was when i downshift or rear break a bit hard my back locks up and skips along the floor.


any ideas?


my rear shock appears to be on its hardest setting but its not solid.