How does the independent dual extrusion work? How do the heads detach and reattach to the belt?

Glad you figured it out. Speaking of nose cones, I made an OpenSCAD script to generate Haack series nose cones, you might be interested: http://www.thingiverse.com/thing:804129

I got a Silhouette Cameo a few months ago to get in on all the hot craft cutting action. Was sad to note that scores were interpreted as dashed cuts. Saw that Cricut had a scoring stylus that wasn't too thick and picked one up today; made this adapter to get it to work: http://thingiverse-production...

Modifying STL files are a pain, at best. You can either use a mesh tool like MeshMixer, or if the STL is not too large and is watertight, you can import it as a body into a CAD program and difference with a cylinder of the appropriate diameter to widen the holes. If the size difference you want is n...

If you have not already, it is a good idea to work through Jules' extensive set of guides covering the collective wisdom of many users: http://forum.makergear.com/viewtopic.php?f=3&t=4711 It may be backlash, but it may also just be that your Z-height and extrusion multiplier aren't calibrated correc...

I spent some time a while ago trying to reduce seams. Made some progress, never completely eliminated them. Decided not to care. I remember reading that some slicer had some clever method to deal with seams, but if you google "seam hiding", you'll encounter tons of people trying to solve the same pr...

Those are some great looking prints. Do you do any modeling yourself? I noticed some two-tone buildings, did you paint those?

I ran some bridging tests a while ago, and came to the same conclusion for PLA: slower is better. It's annoying that perimeters that are also bridges aren't handled correctly; on long runs like that, a sagging perimeter can cause the cross bridges to fail.

Looks almost like a mechanical issue on your Y axis. Check the Y belt tension?

You cut the end flat when reloading? I've seen recommendations to cut at an angle to ease feeding, and have always done that except when trying to save a print by hand feeding a second spool into a running job (never works, by the way).