i have the mystic force shield for snowkite and kitesurf, it rocks, looks great.
the straps system prevents the spreader to go up(kinda useful with a venomÃƒâ€šÃ‚Â²) and the legs straps r very comfortable as well ( don t hesitate to strap them )
i have back problems , it covers a large portion of the low end of the back and i m fine with this seat harness. saves my ribs too
, it has a handle in the back too in case ( not sure if all the mystic harnesses have it)
and more important it doesn t break myyyy precccioouuuussssss
downside: can t be put fast like a waist one. less freedom in mouvements (mainly for no foots and assimilated), as any seat, it s not very fashion looking stylish pro-rider waist harness :p