Hi AScot,
I'm afraid that I can't help you with James Ferguson, but have forwarded your message on to someone who I thnk can.
However, my ggrandfather, John Blue, was on the 1851 census as staying with James at the Portenstuck Inn with his new wife Margaret Ferguson. Could she be James's grandaughter? They are supposed to have had their 1st son, Dugald there, but unfortunately he seems to be unrecorded.
Good Luck Blueth