tablature note heads overlap

[Benjamin]

Hey folks,

Tablature note heads white out the area behind them. When they are simply
overlapping a staff line this looks good, but when they overlap another note
head, such as when two neighboring strings are struck at once, it looks lousy.
Of course I can get rid of the overlap by using small noteheads (\override
TabNoteHead #'font-size = #-1) but that's awfully small. If anything I would
prefer to use slightly larger than the default note heads and do something else
so that the overlapping notes look ok. How would I go about this?

Thanks!

Benjamin