good pickoff pete,

there's an awfull lot of rotational stress on the legs just at the central spine of these, so consider adding the tiniest of struts each side from around the wheel axle up to the side of the back webbing strap( i think some pple have had failures b/c of this). that'll stop the rotation. even 2 rope lines would be a distant 2nd choice(plus one between the legs to stop spread(don't need for the strut approach). Looking from the back, you're making like a little truss like a 'W' with a solid line linking the 3 peaks of the W. (the rope approach links the bottom valleys-hey a bungee and its sprung!!)

-mick