order of articulation symbols

[Stefan Thomas]

Dear communitiy,
I would like to change the order of articulation symbols in the below
quoted example.
But I don't know how to do it.
Here es a short snippet:
\version "2.12.1"
notes = { \repeat unfold 4 {    <b'' g''' >8->-- es''-. <gis'' d'''
>-- fis''-. } }

arti = {
\repeat "unfold" 4 { s8 ->-- %the accent should be above the tenuto,
not below, but how can I change it?
s8-. s8-- s8-. } }

\new Staff { \context Voice << \notes \arti >> }