Hi Carlos,
As Samuli hinted at it is possible to have spengo while keeping java pointed to an ABAP system, there are some great wiki's availble for this that will help you:
Configuring SPNego with ABAP datasource | SCN
Basically its done via attribute mapping, so if you're using the new spnego module you can easly set it in the usermapping tab rather than the visual adminsitrator as it was done in the old module.
Kind regards,
Cathal