G-man,
Big fan here. We have to stop this shoe/foot thing. If you insist on not just leading from the start like you used to be incredible at, this will continue to happen because of your running form. Don't get me wrong, it's a tremendous stride...that that just leaves the heel a little too vulnerable.
Anyway, these comtemporary spikes, which are essentially made up of "nothing" on your foot, obviously fall off quite easily. I have a pair of old Addidas Steeple spikes from the late 90s that have a very rigid rear construction. Most shoes of that era did. Make it a fashion statement or something. The extra 1.0-2.0 ounces won't affect your performance, I promise.