I've searched and found some answers. At one time I remember reading that the triple brifter could be used in double applications, seems it was even advertized in a catalogue or two of the time as an either/or, IIRC.
I've also read that there were some brifter failures because of that 'interchangeability'. If I use the triple brifter for the double is it better to use the small/medium or the medium/large chainring selections to reduce the possibility of a failure? Any difference, I was thinking of using the med/lg (2-3) setting