how much do shackles actual drop truck

[TotalChevy1]

The reason I'm asking is I'm trying to determine if I should go back to stock shackles and de-arch the spring to compensate for the lowering shackles. I've currently have the 1.5" shackles on the truck, but when I installed them I also took and 3 leafs from the stack and the truck dropped about two inches. I though I would get more like 3+ inches. As the truck sits know I'm trying to get an addtional 2 inches. My plan is to de-arch then, but I'm think that I could go back to the stock shackles and De-arch an addtional inch. Sorry this is so long. I guess my question is do the 1.5" shackles actual lower it 1.5 inches or ? on a c20?
Thanks

[XXL]

Generally speaking, a shackle will drop a vehicle half what the measured drop of the shackle is. Ex: for a 3" shackle, you will get a 1.5" drop. This is because you're only raising one end of the spring. The opposite end stays where it is... quick math says that halfway in between the two spring eyes, you will be "half dropped."