Andy, a cross-reference from another variant of Life on Two Wheels, one which confirms the comments above:
I've never used or even held a set of Thorn Touring bars, but a decade-plus ago, when I was spec'ing my Raven, I looked closely at the rise and sweep of the touring bars. They matched almost exactly two motorcycles I had at the time. One was a mid-'80s BMW 800cc touring bike, on which I crossed North America east-to-west and back, and from Ottawa to the Carolinas and back, and covered many other shorter but still demanding distances. The bars were perfect: my criterion of excellence in these matters is that I don't think about them.
The second bike was altogether different: an ex-comp 1957 350cc AJS scrambler, which I restored over a couple of decades, completing it in 2002. I kitted it out for street use, and used an after-market bar which was (near as I can tell) identical to the Thorn Touring bars. I chose this bar before I owned the airhead or even knew about Thorn bikes.
All this to say that there's evidently some common knowledge floating around in the two-wheeled ether, which specifies What Bars Work Well for Comfortable Touring. (Obviously the grips on my two motorcycles differed from the recommendations above.)
Cheers, John
PS: I used drop bars on my Raven, and have them on my Mercury Mk 3 as well -- a personal preference, linked to The Headwind Problem. (Not an issue with my BMW, which had a full fairing. I used the Ajay only for shorter rides.)