Layered staves can create problems with accidentals, in that you may need to repeat the accidental on both staves, which is confusing. To hide an accidental is easy. Simply tie an invisible grace note (with the accidental required) to the main note. See hideacc.nwc (http://www.noteworthysoftware.com/composer/files/hideacc.nwc) (1K) for example.