I just ran across this project on kickstarter. It might cut down on the amount of 3d printed parts required and might help with rigidity.
I don’t know if you guys have issues with keeping the apparatus rigid, but my machine has enough torque to wobble the pipe during G0 rapids so I’ve been pondering ways to strengthen the conduit joints.
Anyways, check this out, looks interesting: http://www.makerpipe.com/about/
-Pete