how much to cut off coil spring?

[Faastone27]

Hey guys I'm in the process of completely rebuilding my front end. The guy i purchased the truck from simply heated the coils to collapse and lower the truck( i know that is totally the wrong way) So now i decided to do it correctly and i ordered 2.5 drop spindles and 1"lowering springs. But i want a total of 5" drop so obviously that means i need to cut another 1.5 " off my coils to get desired drop About how much should i cut off the coils to achieve another 1.5" i think one full coil would be to much? Thanks for your help