A question for you photography and textiles types.

OK I need some help here in regards to white balancing digital cameras. This is job related, but due to the NDA I can’t go into too many details. Suffice it to say that we currently white balance digital cameras using a large piece of white foam board (20” by 30”) and we currently white balance each camera individually. We want to be able to white balance two cameras at a time, but that would require double the white foam board and it has to be able to fold down the middle without having an obvious seam as that stops the white balancing from taking place (no, I can’t tell you why). It also helps in storing the white balance sheet as we would fold it up to put it on a cart.

We’ve tried using white paper, but that invariably creases when folded thus ruining it for the purpose of white balancing. So our next thought was to use some form of white cloth. The question is: is there any kind of cloth out there that won’t develop a serious crease that may interfere with a white balance? Is there anything that photographers make use of that may work in this instance? Any suggestions you guys have would be much appreciated.