The only real difference between this and a stock R100R is the R1100GS 19" front rim. I had it laced to the original hub so I could have a larger selection of DS tires. The fork brace and fender are stock GS parts. The rear shock is after-market, too, although it is the same size as a standard R shock. The windsheild is a rework of a Parabellum from my PD; I cut it down and reshaped it. I'd like to add a set of real DS luggage, but when DS'ing, the bags aren't usually there.
Since the R100R and GS use many of the same components and are based on the same frame, I didn't need to make too many changes to fit my needs. My main goal was to have a bike slightly shorter than a GS that was still capable of traversing most terrain while being comfortable cruising at 80mph. I just finished a 1500 mile round trip to Texas that included rock roads, pastures, and 100mph runs up the interstate. I think it met all my goals quite well.