making the rear flex

SO, I've got an 87 MJ with a 3" long AAL in the rear, it's a skyjacker leaf. It's made the rear very stiff.
I was considering doing a shackle and hope that the leverage will force the leaf pack into working more. WHen wheeling I bet we had 2-300 Lbs of stuff in the bed.
I could do a 1" extended shackle and match it up front with a spacer and have 4" of lift. I suppose that would correspond well with my plans for 32x9.5s
Opine away.
Edit: I should note that I'm not too terribly concerned about the leaf pack health. I will bumpstop so I don't invert it, but it will likely be replaced when I go SOA/8.8

a shackle will give you neglagable difference in how stiff the pack feels the only way to fix that is to adjust the spring rate of the pack buy adding or removing leafs or replacing with thinner leafs. the shackle will allow a large arched pack to travel in the path it needs to but won't help your flex unless it is reaching the shackles maximum swing.

Make sure your ride height is right in between the top out, and bottom out, points in your rear shock absorbers. My old rear shocks were far too short and would not allow droop, which made it ride like crap. I put some longer shocks on where the normal ride height was right in the middle of the shock travel and it rides like an Escalade (by comparison).

shocks came with the lift, they're sized properly. The rear has no limitations, other than the spring rate. After the front gets into the bumpstops it will flex.