Beyond getting my loop-da-loop ramp working decently, I had to redo the left side and move the incoming VUK entrance to the right. I still think the wall needs some work (perhaps open up the VUK on the back too) so you have a better chance of hitting it. I also had to deal with killing any dead zones early (equivalent of having plastics) so that the ball won't get stuck somewhere. So far the ball hasn't gotten stuck any where (at least nothing I couldn't lightly shake the machine to get loose) which isn't bad for cardboard walls.
Here's a video showing the latest gameplay: