I am using SimpleMembership (http://blog.osbornm.com/archive/2010/07/21/using-simplemembership-with-asp.net-webpages.aspx) but I am unable to have place my custom user table
I think the key is that it will use whatever the default schema is associated with your user id. In SQL Server, you might try specifying a default schema other than dbo for your user account and then I think it will create the tables in that schema, but I don't think you can specify the schema on the call to InitializeDatabaseConnection.