6 and 8 string tab

[Walt North]

I occasionally write out Tab notation parts for 6 or 8 string lap steel 
guitar. I have created tuning entries for these and it works well using 
Minimum fret and max fret difference values.  Here is my question. 90% 
of the time I only need the upper six strings and just occasionally dip 
down to the 7th and 8th strings for a few notes. Which means most of the 
time there is unneeded page space used up.  I could use different tab 
staffs intermittently  but that gets pretty cumbersome when it is only 
be an occasional note or two.  And I've never been able to get things 
realigned vertically when going back and forth  between 6 string and 8 
string tabstaff.

Is there any approach that would add just a lower tabstaff line for the 
7th or 8th string as needed - similar to the way ledger lines are added 
to regular staff when the notes go down to middle C or lower?

Maybe something with markup?

Walt North