This sounds like a classic case of extremely hard knuckles. Take your voicing tool and experiment on one of them by driving the needles through the leather and into the core. You should get some major changes immediately. Don't be surprised if you'll need address this same issue in a year or so. It's the nature of these types of knuckles to pack down hard.
Tom Servinsky
I have had minimal results with needling the buckskin with my sugar coater but I will try a single needle all the way through as you suggest. The core material appears to be dense felt and I was able to easily penetrate if from the side with a needle.
Gene
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