wow....just talked to ALCAN, and they told me bad idea! told them what i wanted to use it for and they said it would walk all over the road and not to use them for rear shackle mount...even with a waybar...hmmmm 
Shackle mount NO, but you should not have a problem with them in the spring cause the frame side will keep the shackle from leaning and causing the rearend to move from side to side.
