Unacceptable to who? Them? They're probably out shaving a ram's undercariage for proper Tups Indespensible dubbing or flipping over vixen foxes to see if they're incontinent. so they could score proper Hendrickson dubbing. As in everything fly-tying related, unless you're trying to sell flies or are tying in competition, you are free to tie however you like, using whatever materials you enjoy using.
Regards,
Scott