Programmatically adding web parts to pages - audience targeting

For easy deployment of web part pages we have build a tool to add web parts to pages, using the SPLimitedWebPartManager feature.

For some web parts we wish to control audience, and to my luck I came across this page describing how to do this. However, understanding the AuthorizationFilter is a challenge.

Reverse engineering is probably the answer ... will update once I have figured this out.