Stalking Fox, like String Stretcher said, stay away from the vulture feathers, and any and all of the raptors, eagles, hawks, owls. Do you live near the woods? are there turkeys in your area? A little cracked corn, uh..... accidentally spilled.....
in the area they frequent, and you should be able to find feathers there, that they shed normally. If not, then is there anyone who raises chickens, geese, ducks, turkeys, peacocks, guinea fowl, etc. The wing feathers of any of these will work well. Turkey is much better, but if you don't have access to them, try the others. You won't be able to make the high style of fletching, except for the wing feathers of the Peacock, but they will make good fletching. Oh do you know of anyone who has a parrot, or cockatoo? When they molt, they have nice feathers also. Do you have a turkey season ? Use a gun, and then you have the materials, plus fine eating.
I have Turkeys come in my yard regularly and every now and then, they lose a feather. I also gather them in the fields. We have LOTS of wild turkeys out here! I have some wing feathers from the one group that comes here daily, when they were about chicken sized or so, and the are the perfect height for my style of fletching. Anyway, I hope that helps, and for a heavier and stronger spine weight, you might try using fiber glass resin
, on your shafts.
As string stretcher said, wrap those areas. Also, I would recommend that you use a smaller diameter thread, like upholstery thread, and cover all of the wraps,with super glue, or pitch glue, and smooth it out, so there is a smooth transition from the arrow head, to the shaft, and there is nothing to grab and slow the penetration. Also it water proofs it.
As Lost Arrow said, your body is arranged in a very well thought out process, and you can use arms, and such as measurements. For instance if you have normal arches, you can measure from the wrist joint, to the inside of your elbow , and that is your foot size, and from the wrist joint to the armpit is your inseam. Some kind of nifty designing thought went into the making of the human! Of course there are some areas where the chief engineers left for lunch, while the new guy stayed, and proceeded without them.
Good luck with the search for fletching, as a last resort, trade, or buy.
Wayne