On 1/2A type planes, when I still had a 72MHz radio, I have coiled the antenna wire around a piece of plywood and secured it. Like you said, be careful not to wrap the wire back over itself. I know it did technically shorten the range but it was still good as far as I could see and fly the airplane. On something like the Waco I would just runit out the tube though and let the excess stick out if there is any. It can always be taped to the fuse or something too.