Thanks for reporting back.  Sometimes a thread dies and we don't know if the problem was solved or the poster gave up.

As is usually the case, once the problem is found, the symptoms make sense. 

Apparently when the SCV was active, its internal load sense line did the job of "opening the pump up" which then provided the flow/pressure necessary to provide good auto steering.  With the double disks, the system was not tripped up enough.