SQL RS Custom Authentication and WSS

I am trying to implement custom authentication as per the instructions in the following documents:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsql2k/html/ufairs.asp

http://www.devx.com/dotnet/Article/27133

But, I was able to make it work without Windows Sharepoint Services(WSS) but not with it.
I was wondering that has anyone tried to extend the security of RS and make it work with WSS installed on the same machine.

My Machine information is:

1. Windows 2003 Server
2. SQL Server 2K with SP3a and SP4
3. SQL server 2000 Reporting Services
4. Visual Studio .NET 2003
5. WSS

I have tried to get a workaround WSS problem for almost 2 days now and nothing seems to work.

The reason I want to have my own security extension for RS is that I want to use RS from an existing Web Application which has thousands of users and we already have our own authentication mechanism for it.
We dont want the Reporting Server to be run from one specific Windows account or by the annonymous user IUSR_MACHINE Windows account.