Prusa MK3 hard foot

Was trying to find a fix for the vertical lines in the printing on the MK3. There is a thread in the Forum on bracing the Z axis. The printer comes with some soft low hysteresis flexible feet and this looked like a place that would excite the z frame about the x axis and result in artifacts in the print. I just did a quick set of "hard" feet to replace the rubber ones and noticed an improvement in the condition. These were printed in pla @ 50% fill rate. There is a recess in the bottom face to a