Spacing isues in polymetric music

I am trying to typeset a piece that includes a repeating part that loops independently of the other music. I have been partially successful using the documentation relating to polymetric music (see example_one.ly which, hopefully communicates the musical idea that I am hoping to achieve). This feels like a bit of a hack though; if I leave 'Default_bar_line_engraver' out of the bottom Staff context bar-lines print as I need, but if I remove it explicitly the output is incoherent; if I implicitly include it with "\consists" barlines are drawn at seemingly unprecitable locations.
The biggest problems I have, however, are spacing issues (apparent at the bar-lines in example_one.ly) that become much more obvious as soon as the music becomes more complex (see example_two.ly).

Is there a way to have a staff with note spacing that is independent of the others in the same staff group?

Thanks again to the list for the freely offered expertise and thank you to Torsten for your help solving my issue with custom glyphs - I do not seem to receive direct email notifications from the list (yes, I have checked my junk mail) and it seems inappropriate to clutter the list with new 'thank you' threads.

Cheers,
delboh

From:	Ebo H
Subject:	Spacing isues in polymetric music
Date:	Thu, 24 May 2018 21:44:23 +0000