2 vBulletin forums sharing same user database?

How would I fix so that 2 vBulletin forums share the same database?

And do not tell me it is not possible, cause it is.

http://MMOwned.com http://FPSOwne开发者_开发知识库d.com

If it's just a predefined set of tables that you want to share you may be able to use the FEDERATED storage engine to "share" a table across two separate databases or perhaps the MERGE storage engine to effectively share a MyISAM table across two databases.

I'm not sure what fun and games you might run into with counters, etc inside vBulletin.

Have you had a good look on the vBulletin.org forums or asked the owner of mmowned.com how they did it?