A couple of things to consider... Hackle has come so far in the past 15 to 20 years that most of the literature about it doesn't apply as much unless you are still using old hackle. In regards to stiffness, saddle and cape hackle are identical if you are using high grade hackle, and I bet it could be argued that some capes are stiffer than saddles depending on the products being tested (it's all relative). Also, in regards to "cone" shaped hackle... That is caused by the hackle feather being too short with very little sweet spot. Most of the hackle from today is long enough to get two to three flies from a single feather, so fibers are all identical in size for the whole (long) sweet spot.