[Fot] Electronic Distributor and Total Advance

[T Thompson]

I recently purchased a True Spark Programmable Distributor.  My Mallory Dual
Point had so much play at the top of the shaft (thanks to Mark Eden for
noticing this) that the point gap and dwell was very erratic at high RPMs.  So
I went with the True Spark that Mark had bought as well from BP Northwest.
 
My question has to deal with the bushings included with the distributor to
adjust total advance.  We obviously can't do static timing and at idle it is
likely there is some degree of advance occuring already (I can't idle down
to 500 rpms with the cams we run).  For now, I have installed the distributor
with no bushings and set the timing.  That is to supposed to give me 30
degrees of total advance.  It starts missing at about 5000 rpms.  My next step
was to try retarding it more to see if that helps.  
 
My question is how to
determine which bushing to use, if any, to give me the best performance.  I
don't have a dyno or a racetrack in my back yard, so I was wondering if anyone
else is running this distributor, and which bushing they may have used.  Total
advance is configurable from 18 to 30.  
 
I was thinking of just getting as
low of idle as possible and seeing what the difference is advance is between
that and my preferred total advance, but then I thought someone else on this
group likely runs the same distributor and may get me closer.  Bought the
distributor from BPN. Part number is 41427HP.
 
The good thing now is that
when I do set the timing, the mark on the pulley does not fluctuate (at all). 
Before it was hopping all over the place.  
 
Thanks in advance for your help.
 
Ty