At last! Here's the long-promised X-Carriage for my dual extruder http://www.thingiverse.com/thing:34821. This is a slightly modified version of Greg's X Carriage for the Prusa. I've also added a mount for dual nozzle cooling fans. A print cooling solution will be coming soon. Can actual dual-extrusion printing be far behind?Besides the obvious, you'll need two 25mm, 12V fans. Print and assemble the carriage in the usual manner. (See the original by Greg.) The fans are mounted with M3 bolts. The fan mount is a tight fit. One end hooks on; the other gets a zip tie or an M3 bolt. The dual extruder fits easily into place and is held with M4 bolts.