Appologies in advance for using NWC2 Clips in this forum.
This may work. Create 2 staves with the same midi channel and put the following Clips on them.
A recorder and an oboe duet on one channel! (a least it is with my AWE32). Since you are doing choral music, the 64th delay should not be a problem. You may still have the note collision problem.
!NoteWorthyComposerClip(2.0,Single)
|Instrument|Name:"74"|Patch:74
|Note|Dur:4th,Slur|Pos:4
|Instrument|Name:"74"|Patch:74
|Note|Dur:4th,Slur|Pos:3
|Instrument|Name:"74"|Patch:74
|Note|Dur:4th,Slur|Pos:2
|Instrument|Name:"74"|Patch:74
|Note|Dur:4th|Pos:1
!NoteWorthyComposerClip-End
!NoteWorthyComposerClip(2.0,Single)
|Rest|Dur:64th
|Instrument|Name:"68"|Patch:68
|Note|Dur:4th,Slur|Pos:2
|Instrument|Name:"68"|Patch:68
|Note|Dur:4th,Slur|Pos:1
|Instrument|Name:"68"|Patch:68
|Note|Dur:4th,Slur|Pos:0
|Instrument|Name:"68"|Patch:68
|Note|Dur:4th|Pos:-1
!NoteWorthyComposerClip-End