To the best of my knowledge Chapter 4 is only applicable / required at a handful of noise sensitive airports.
I suggest that when chapter 4 is not required you operate to next lower certification.
When certified to chapter 2 you must follow the specified chapter 2 procedure.
When certified to chapter 3 you may follow the specified chapter 3 procedure but nobody will complain if you use the chapter 2 procedure.
You can be sure that non-compliance with a SID will be noticed as it is closely tracked by radar.
Non-compliance with a NADP takes a lot more to prove.
Last edited by dusk2dawn; 5th Mar 2015 at 20:42.
Reason: Forgot something