Articulated tails: What the heck am I doing wrong?

I am trying to make a beautiful, swaying, graceful dragon tail, but I am having a lot of difficulty getting that effect.  I'm hoping to get some input from people who have had success with this sort of thing!


Here is my inspiration:
http://rarsuit.livejournal.com/44876.html<--- Relevant tutorial
https://www.youtube.com/watch?v=6pvdnCLW0O0<--- A video of CC showing off an articulated tail

Here's what I have:

Please excuse the sun fading; I accidentally left it outside.  The whole thing is about 26" long and 6" at the widest.  The foam is Super Soft foam from foambymail.com.  It is the softest, squishiest foam I have ever handled.

Here is a cross-section drawing of what I did.  I hollowed out the foam as much as I could, but it touches down at every segment of the skeleton.


Lastly, here is a video I took trying to get this thing to sway.
https://www.youtube.com/watch?v=DrDkvNiqbG4

As you can see, it is very stiff!  When I put it against my butt, it is very difficult to get it to wiggle.  The videos I've been seeing are of tails that sway with little to no effort by the wearer.  I have a few hypothoses as to what the problem might be, but I would really love to hear from other makers before I use up more materials.

1. Should I make the tail longer (or skinnier)?  This tail is only 26 inches long, while the examples I've seen are a yard or more.
2. Should the foam touch the armature less?
3. Is there a better foam to use?  This is seriously the softest foam I have ever touched, I thought it would be a winner :/
4. More weights?  I'm afraid of making this thing too heavy, but if that's what it takes...