On my D800, I have the CF slot as primary and SD as secondary. I have secondary set to RAW + JPEG which plants the RAW images on the CF card and JPG on SD as long as both cards are installed. If I pull the CF card, the SD card gets both RAW and JPG.
You may want to set your SD as primary and set the secondary to overflow or backup but not RAW + JPEG. Then select image quality to JPEG. Hope this helps.