The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Go online to Jim's Fly Shop at the Campfire Lodge in MT...Look at the famous "Wall of Hackle"...They are nice folk there and will give you the straight skinny on what's what if you give them a call...Great hen sets as well if you are tying any softhackles...
Another factor was we had had a bit of scotch before doing the surgery, but I'm pretty sure we got an accurate measurement.
When I was in my formative fly tying years I used to only buy Metz rooster capes. I agree there are a bit more variation in the sizes of flies that you can tie but once you get below that sweet spot about 3" - 4" down from the very top of the neck the feathers are so long and webby that they are only good for folded hackle legs and beards or palmering hackles on woolly Buggers or making streamer wings. I will admit though that on good to very good capes, on the sides of the capes, you can usually find short hackles with very stiff barbs which are great for tailing dry flies. I guess they are called "spade" feathers but I'm not positive.
As I grew older and refined both my fly fishing and hence my fly tying I realized that 90% of all my dry fly tying was in sizes #14 - #20. So I stopped buying rooster capes and started buying the saddles only. I always would buy either the #1 or #2 grade. The feathers are 6"- 8" long and I can tie 4- 6 flies minimum from each feather. One saddle each in sizes #12 - #16 and #18 - #22 will cover almost all of my dry fly work. I don't have a zillion colors and still catch at least as many fish as the next guy. I have saddles in medium dun, light dun, honey dun, cream, grizzly, coachmen brown. You can either buy the entire saddle, a half, or a quarter. Or if you have a tying buddy you can buy the complete saddle and carefully turn in over skin side up and cut it in half with a razor blade.
The feathers are 6"- 8" long and I can tie 4- 6 flies minimum from each feather.