... For a top plate, I recommend that you tune the plate before you cut out the "ff" holes. cutting out the sound holes will not change the actual frequency but it will change the overtones; it is easier to tune the plates now. Notice the sound post pad which was left slightly thicker.
...I would now just make plate thickness 2.6mm all over and eliminate this pad.
...You will notice that here I have drawn on the Vigdorchik tuning strips (in pencil) but this is for a final adjustment and/or check of the evenness of the plate.
...Now suppose that just the outlined area is too high in tone compared to the rest of the plate which is at the frequency that we want it to be at.
...In this case, tap the too high area with your special tapping pencil and hear where it is the highest frequency. Beginning there, gently sand or scrape this area widening out as this area is lowered until the entire area matches the rest of the plate
...The rule for adjustment is that the entire strip (that is the center of the strip except the wide middle strip which is made all even) is raised or lowered by scraping or sanding just the outer edge of the strip as shown. One side to raise the tone and the opposite to lower it. Just the least little bit of wood removal makes the necessary adjustment (perhaps one to three grams for the entire plate).
The blue area shows how much area is scraped to actually adjust a strip (in this case to lower the strip)..
Scrape near this edge to lower the strip tone
...You will notice that the end of the strip nearest the center bout is the side which is lightly sanded/ scraped to raise the tone of that strip.