I shoot with very long lenses and I tend to be a fanatic about vibration control. I agree with your observation that vibration is too often overlooked as the culprit in soft images. When I test lenses for sharpness, I generally use multiple flashes very close to the target as my "shutter" to eliminate any vibration contribution to the image. Nonetheless, I'm somewhat surprised that you noticed a remarkable difference using MUP at 1/800. I would have expected a slight to barely noticeable difference, though at 85 meters with your subject viewed at 100% I expect you would see the difference.