stem length of eighth & 16th notes are too long.

[MING TSANG]

Please check the stem length on voice one BASS cleff is too long. 

Did I do something wrong?

How cab I shorten it?

Attached is snippet and png.  I have trouble produce the snippet exactly as the png.

I try "\override Stem #'length-fraction = #(magstep -3)", but it affects stems on quarter notes, half notes but not on eighth & 16th notes.   What must I do in order that the stems for 8th & 16th notes can be shortened also?
 

Blessing in+,

Ming

i-just-snippet.pdf
Description: Adobe PDF document

i-just-snippet.ly
Description: Binary data

2012-02-28_073755.png
Description: PNG image