Just to complicate matters the radius may be different at the bridge end of your neck and at the nut end (Composite necks) as if life wasn't complicated enough ! I got a really good book by Dan Erlewine called the Guitarplayer repair guide and he covers this and other topics in some detail..... 23 bucks well spent ! He is the same dude that hosts the stewmac guitar wiring video I was banging on about earlier