The only answer I've found is to precalculate the number of categories there will be in the result set, then set the size of the chart SWF accordlngly.
In my JS, I pass in the numberof categories, then do:
var height = 60 * numEntries;
var chart1 = new FusionCharts(charturl+charttype, "chart1Id", "600", height, "0", "1");
The results look pretty good.
(see attachment)
Larry