expressive marks alignment, accent position

[Germain G. Ivanoff-Trinadtzaty]

Dear all,

1) In the following snippet, I'd like the accents to be placed above the 
staff :
{
d'1-> d'2-> a'-> a'1->
}

2) Here I want all the accents be aligned (horizontally), outside (above) 
the staff :
<<
{d'1-> d'2-> a'-> a'1->}
\\
{d'1 d'2 a' a'1}
> >

I played with :
\override DynamicLineSpanner #'outside-staff-priority = #250
\override DynamicLineSpanner #'staff-padding = #4
\override Script #'staff-padding = #4
\override TextScript #'staff-padding = #4
with no positive result.

Please point me to the relevant LSR/doc chapter.
Thanks,
G.

(expressive marks alignment, accent position, alignement des articulations)