layout for song in 9/8

[dflat]

Adding a single barline at the right of the last space of a system will automatically add a barline at the beginning of the next system on the left (and vice versa) as you have found.

You could try this:
Insert one space at the left of all your systems and do not use the last space of each system at the end (right.) Effectively this means you have an indented margin of a space (or more on the right) inwards from each end.

From my quick tests, this test song plays ok (3 spaces per measure).

Here is the song:
9-8 song - Unknown Composer

[I would consider all this a workaround at the moment because in the future the song code and playback engine could change, causing problems.]