Whole note tremolo issues

[Panteck]

Windows XP, Lilypond 2.8.1-4

Whole note tremolos look really bad, but quarter note tremolos on the same 
pitch look fine:

\version "2.8.1"

\score
{
\new Staff
{
 \clef bass
 \time 4/4
 \key c \major

 a,1:32 b,: c: d: e: f: g: a: b: c':
 \break
 a,4:32 b,: c: d: e: f: g: a: b: c': r2
}
}

--Steven

Tremolo.PNG
Description: PNG image