I found lots of issues with thing:19026 when I tried to slice it. The positioning of the parts in the model appeared to be eyeballed and it required a lot of unnecessary supports. This one should print without support, and of course it's completely parametric.

with the experimental firmware and upgrades that are on my bot right now, I haven't managed to finish a print of this yet, and I probably won't get another chance to try for a few days, so I thought I'd post it now and see if anyone else wants to try.

Here's a visualization of roughly what it should look like in action: https://plus.google.com/105535247347788377245/posts/cB7JWab1Mo4