decreasing spacing between staves

[Eric Flesher]

Greetings,

I've looked high and low for the solution to this (rather basic, IMO) problem,
and seem to be coming up empty-handed:

I have a score that requires a single-line tablature staff above the main staff,
which contains pitches. I need to find a way to decrease the space between the
tablature staff and the main one such that it generally is not more than 2
spaces (i.e. staff spaces) above the main staff, but yet will move higher if
needed to avoid collisions with leger lines, articulations, etc. Noteheads
between these two staves will typically be beamed together (i.e. cross-staff
beaming).

Adjusting the minimum-Y-extent of VerticalAxisGroup does not seem to have the
desired effect (staves are too far apart); adjusting offsets in 
NonMusicalPaperColumn is possible, but only doable at the very last stage, i.e.
once all other input is done. 

So, is there an easy (and hopefully intuitive) way to decrease space between two
staves (even if the score were to contain more than 2 staves) globally, without
having to set system breaks, such that the layout will default to a narrower
vertical spacing for those staves?

Thanks,
EF