Now I feel stupid. ;-) I did so much thinking ahead of time about how I wanted to build my UDS, but didn't even THINK about cutting the expando one way or the other... I just started marking and cutting. Of COURSE it's easier to bend in the other direction! How much easier? Well, I just happen to have the tools in front of me to figure it out... LOL...
So, here I go with a major egghead move:
This model shows two pieces of expando with one edge magically glued to a wall and 20 pounds hanging off of the other end of the piece, and the displacement numbers show how far the end of the piece sags under load. It turns out that expando is 5.2 times stiffer (and therefore stronger) if you try to bend it the way that I did. In other words, BEND IT THE OTHER WAY!
I knew it shouldn't be as hard as it was, but I didn't know I was doing 5 times as much work as I had to!!!
So, now that you all have seen me wrestle with that expando, you know what NOT to do.
Glad I could help.