Why are long shackles not 4by worthy? I really see no problem with having that long shackle other than it will catch rocks and look cheesy. You will have a ton of droop from the axle and you benefit from the longer length of the spring without otherwise having to remount the hangers. I would rather have the long shackle and retain the flex than run a add a leaf or remount the stock springs. I would encourage you to flex out that setup and see how good it works before you put add a leafs or some other junk in there. I would keep it until you can do it right.
