\version "2.13.8"
mm = \relative c'' { c2 c c c c}
dd = \notemode { s2\f s s\p s s\f }
md = \relative c'' {c2\f c c\p c c\f }

\score {
\new PianoStaff <<
  % That's how the pp should be aligned horizontally:
  \new Staff \md
  % Unfortunately, attaching the dynamics to skips will position them too far to the left:
  \new Staff <<
    \mm
    \dd
  >>
  % With the new Dynamics context, unfortunately, attaching dynamics to skips
  % is the default, resulting in ugly dynamics position (i.e. dynamics touching 
  % the bar line!)
  \new Staff \mm
  \new Dynamics \dd
>>}