This feature needs to be finished (there is somethig donde, but not a setup GUI, and it's not working on realtime).
We want finish fix all 1.0 bugs, to release the stable version first.
but make sure that feature is already planned for next 2.0 version.
if you want to try what's done, you can edit the tuxguitar configuration file:
i'm not sure where's the "user.home" under mac..
i think it's same as on linux:
/home/[your_user]/.tuxguitar-[version]/config.properties
on that file, you should add:
score.line-spacing=value (default is 8 )
tab.line-spacing=value (default is 10 )
That should change the tablature/score scale.
It's important you close tuxguitar before edit that file, because tuxguitar will re-write when close so will override your changes.