I also believe that I am descended from the Ardnabie line of MacDonell/McDonald, straight down the paternal line, i.e. father to grandfather to great grandfather, etc.
I would be interested in any information that you may have on the Ardnabie branch in Canada. I have not yet been able to find a copy of the book by Duncan Darby MacDonald.
I would also be interested in finding someone who believes that they are descended down the paternal line who may have been tested through FamilyTreeDNA so that we might compare our results.