LOL, sorry had to smile at that. Yes the flank is the sides. I can tell you have never been in the military, LOL! Otherwise you would have learned a lot of commands like Left Flank, Right Flank and so on. Look at the soft feathers most. You could pull the barbules off some of the stiffer feathers if you wanted to make a short tail. Also yes. Think the tail feathers on a Mallard sould be great! If I knew how to collect the CDC I would tell you, but I am just not good at finding them, but would be near the oil glands and very thin feathers, but use a lot if fly tying and could also tie a jig with them if you want, but needs to probably a small jig.

forgot to add if you get any geese the CDC is bigger and better!