This is a limitation of the Webcharts engine and a common problem among
I assume you do not wish to use a different tool ($ or time).
Here are some techniques we've used to mitigate this problem:
1) Turn labels off -- User gets precise number in our own, external legend and
2) Use large chart size with small font size (6 or 8 px).
3) Aggregate small slices into an "Other" or "Misc." pie slice. Several
slivers become one "Misc." slice. The bigger and important things are still
shown seperately. We break out the details on drilldown and/or mouseover.