ties problem

[libero . mureddu3]

Hi list!
In the following snippet I would like to tweak the appereance of the ties
in order to avoid collision. I want to ask your opinion: is it better to
move to the other direction the middle tie, or just move a bit to the left
the two upper ties?
And in both cases, wich parameter I have to edit?

Thanks
Libero

lilypond 2.4.5
macosx 10.3.8
ibook g3800

{ < g c´ d´ >8~ < g c´ d´> }