So I love love LOVE Silver downtube shifters. I actually more often use the Suntour Sprints that the Silvers copy. I've got them on 4 bikes at the moment, 3 as downtube shifters and on one bike configured as barcon shifters. The only gripe I have about them in the barcon configuration is that they look and feel a little too long. I finally took some measurements and sure enough, Shimano barcon shift levers are about 65mm long, while downtube shifters are more like 76mm long.
So, when Riv started selling the S&S thumbshifters I got an idea. I'd buy the S&S shifters, use the levers as barcons on one bike, and use the clamps as the base for Shimano indexed barcons on another bike.
I haven't done all the setup yet, but I took a few pics of the idea and the comparative lengths. These S&S silvers are cut down to 67mm and have a rubberized lever. I think these might be the perfect barcon shifter now. I'm really excited to put them to use.
The clamps with the shims that come with are equally exciting for my Bombadil cockpit ideas. I feel like George Peppard "I love it when a plan comes together"