\version "2.16.0"

\header {
  texidoc = "Stems reach correct begin points of merged noteheads.
"
}

<< { \aikenHeads f'8 }  \\ { \aikenHeads f'8 } >>
<< { \aikenHeads f'4:32 }  \\ { \aikenHeads f' } >>
<< { \aikenHeads e'8 f' s4 }  \\ { \aikenHeads e'8 f' s4 } >>