Chuck, you are absolutely right. This would be the kind of data that could be compared to "felt" recoil by a panel of various size and sensitivity people. Possibly, you would be able to correlate curve characteristics to subjective "feelings." Perhaps you would find some shooters sensitive to recoil acceleration, some to recoil velocity, some to recoil displacement, and some to recoil force. And, there may be other factors.

If we had load by load time-pressure curves, I think we could calculate acceleration, velocity, displacement, and butt plate force. The shoulder contact area over which the recoil force is acting may also be important if we find that recoil pressure against the shoulder is important.

I suspect that G. Thomas's recoil study is accurate. It is unfortunate that he didn't include data so we could check this study. Unfortunately, he wrote for an audiance that generally didn't "peek at the works." Only recently have there been gatherings of "shotgun geeks" to slice and dice everything ever written, sift out the truth, preserve it, and then extend it.