I was thinking the ridged would have to be a good fit for it to produce a consistent finish.
You'll tamp to a level that's below the grouphead. Once water is introduced, the puck swells to fill the void, and those pretty ridges disappear.
I've used the convex & flat tampers on back to back to back to..., and couldn't discern any advantage one had over the other. When the ridged tampers came along I laughed out loud at the prices tamper makers were charging for this
improvement.
:laughing4: