[PD] _tight_ midi clock sync

[sven]

hi all,
i'm trying to get some midi sync working with pd as the slave.
receiving clock pulses via [midirealtimein] works so far.
ive made a sequencerpatch which uses 1/128 notes as its timebase.
the midi clock sends a pulse every 1/96 note.
the variation of time passed between two pulses (measured w/ [realtime])
is much too big to get a 1/96 to 1/128 conversion working.
but even a tight sync to 1/16 is impossible as time measured varies by +/- 
5ms per 1/16 at 120bpm.
thats on win xp.
when i send note-ons to pd instead of using the midi clock i have the same 
problem.
what can i do to get my sequencer tightly synced?
sven.