riverrat,
To answer your question, the McKesh mirrors are the best of several types of towing mirrors I have tried, although I have not had a pair of the three arm mirrors you referenced. None of these add-on mirrors are totally satisfactory as they all tend to need adjusting or tightening from time to time.
I have seen pictures of the Leer shell in photo's submitted by Honda Ridgeline owners at
www.ridgelineownersclub.com/forums and they are neat. You have a nice set-up with the Thule rack, and all. Do not want to continue Ridgeline talk here in the TrailManor Forum so you can use my e-mail address if you would like to chat further.