Duane just to throw in my 2 cents. In a touring bike I would never run a DD6. I would run only and OD6. You touring bike is on highway most of the time. IMHO that is the only time you will use OD.
Mike - gave it a lot of thought before I picked one over the other.
The advantage of the DD is that it is relatively easy and fairly inexpensive to change the overall ratio. Your talking a one time cost of a primary chain and comp sprocket, a gasket and oil and a couple hours work.
Should I decide to add a trailer for the bike this was the route I wanted to go.
Could also change the primary gearing which I would have done had I gone the OD route.
I didn't do this for the gas mileage - did it 'cause I wanted too.
If I can tailor the gearing to my riding style with just the comp sprocket, then this is good.
Of course - if I don't like it - I already have the tools - I can revert to the stock 5 speed and sell it on eBay. And everyone can say "told you so".
Wouldn't be the first time I put some thing on and then changed it later - did I mention how many seats I have gone through?