2 inch drop shackle.

My 2006 crewcab has a flipkit in the rear, which is 6 inches of drop. I want to lower it 2 more inches in the rear for an 8 inch drop.

All I need is a set of drop shackles, correct?
http://www.thesuspensionsource.com/...ram-1500-all-97-03-ford-f150-all-2-rear-drop/

I was reading some stuff about how drop shackles sometimes raise a truck, so I'm a bit confused, and just wanted to make sure all i need is a set of 2 inch drop shackles.

Thanks guys.