Thanks for the comments chaps, appreciate it.
These are dead easy to make, will add to the list of video's i need to make at some point.
Thickness wise they are prob no more than 3mm thick at the base of the feather by the quill, tapering to next to nothing at the tip, bonus with these is when you carve them, if bit of wood cracks or splits off, it doesn't matter as it just makes the feather edge look better, some of the gaps and voids you want and therefore you carve deeper so you come through the other side, sometimes the tattier the carving the better the feather looks.