Put it in a stocking, and wrap it in newspaper.
Well, you really don't want to put a kink in the shaft of the feather, but a slight bend can be fixed with some warm water and some manipulation. I would just suggest using a larger bag, possibly a 2 gallon bag to keep the tail straight. I have taken two pieces of cardboard and placed the tail of an old squaw and pheasant between them, and then taped the rim of the cardboard, but that was to ship them from my hunting destination home, and may have been overkill? If I was just keeping it in the freezer until I saved the cash to get it to the taxidermist, I'd just put it in a larger freezer bag and keep it on a shelf by it's self, keeping the feathers straight. Don't store it under the pork chops!