or just change the grace notes on the bottom staff to quarter notes.
I don't see why a layer is needed here. This:
!NoteWorthyComposerClip(2.0,Single)
|Chord|Dur:16th,Grace|Pos:4,n6|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:5,7|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:2,6,b8
|Chord|Dur:16th,Grace|Pos:4,6|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:5,7|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:2,6,8
|Bar
|Chord|Dur:16th,Grace|Pos:n3,5|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:4,6|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:#1,5,7
|Chord|Dur:16th,Grace|Pos:3,5|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:4,6|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:1,5,7
|Bar
|Chord|Dur:16th,Grace|Pos:2,4|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:n3,5|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:n0,4,6
|Chord|Dur:16th,Grace|Pos:2,4|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:3,5|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:0,4,6
|Bar
|Chord|Dur:16th,Grace|Pos:#1,n3|Opts:Stem=Up,Beam=First
|Chord|Dur:16th,Grace|Pos:2,4|Opts:Stem=Up,Beam=End
|Chord|Dur:4th|Pos:0,n3,5
!NoteWorthyComposerClip-End
seems to be what you want.