I was looking at the Sport Plast collapsible field decoys, and I see a common problem with these is that they don't stay to their true form. They come collapsed and take some maneuvering to get them back. My question is, has anyone tried filling these things with expanding foam i.e., Great Stuff? These decoys do not look bad in my opinion, and if the expanding foam idea is plausible I might have to get a dozen or so just to try them out. Do you guys feel they are worth buying or just a waste of time?