dakota lift shackles

I know most of you guys don't like lift shackles, partly because they allow the springs to move about and flex more then the stock set up

so, what do you guys think of these?

http://www.ebay.com/itm/262355001086?item=262355001086&viewitem=&vxp=mtr

(I send the seller a message to ask about specific measurements)

but it sure looks like these would at least prevent the flex, no?