For this year, I would probably go either mid April or in July to get that flow range. It all depends on the melt, but by mid april, the Yampa should be starting to flow which will bring up the Green, and low elevation stuff should bring up the Colorado main stem, so I bet you could find yourself in the teens. Likewise, hitting it all after peak in mid-summer should still get you medium flows, given this year's bomber snowpack.
Definately would take some cajones to hit that stuff at peak this year. That shit's going to be BIG. Anyone here going to hit that stuff? I'm already looking forward to the videos!