I mean, right there, the guy says PLASTIC IS BETTER. and WOOD drifts.
kawai take note. Wood = Calibration Drift.
if they're going to stick with the unstable material, they must release a recalibration-Jig, so people can recalibrate the grandfeel actions at home.
it's also important to have a reinforced calibration rail installed where the jig can mount, otherwise you can't rely on the majority of frame surfaces for flatness (relative) to the keybed.
