Well, I did do a cardboard box test and was very positive! I see what you mean about flex and I think you're right, but I think I had about as good a test as I could. At first I wasn't looking forward to carving up some Amazon shipping box, but then I realized I had something better...the box they came in! Duh. So I just slipped them back into the container they came in, and while I think I'll get more bass from a stronger surround, I was already much more pleased with the results.