As it is now lodged in your mind and may impair your enjoyment of the P3 (lucky chap) maybe it would be worthwhile demonstrating the 'cracking sound' to an engineer experienced on the type. Hopefully he will be able to put your mind at rest without emptying your bank account
As an afterthought, how old was this article? Were they referring to aircraft with wooden main spars or was it a general statement covering all aircraft construction methods?
I waggle the wings before I fly just to make sure they're screwed on. I get some creaks but no clunks. Clunks mean something lose and pushing the bird back into the hangar!!!!