BO and SAP Netweaver Portal sso

We want to show the BOBJ reports in our SAP Netweaver Portal system with SSO functionality.(without sign on screen pop-up)

For this purpose we have integrated our SAP ECC system and BW system with BOBJ 3.1 enterprise system.

We also found in BOBJ we can select one default system for SAP authentication.

In our Portal system we are using ECC as the umebackend (user database).

Our issue is when we switch the default system on BOBJ to BW system the authentication fails(As the user is only present in ECC system).

What we want is whatever is the default SAP system ECC or BW, if the user is present in any one of the system he should be able to view the report? Or is there a possibility of trusted connection between BOBJ and SAP systems which can surpass all this authentication?

Also note we canu2019t use SNC at this point in the project because the client does not have SNC license now.

Please help me with some information.

Regards,

Neni