The CF burgee is a typical yacht club size, 12" x 18", which I think is fine. I have one and it is very high quality. Any larger and it might start to look odd and out of place, in addition to being more expensive to produce.
A sticker would be great. It would not necessarily end up on boats transoms but then wherever it does end up just might help in increasing the forums
name recognition. I could not put one on the transom of the university owned research
vessel but I would put one on the back of my truck and car. Perhaps start with a small number of them and see how well they sell?