Change code to work with 20x4 LCD instead of 16x2

i have your first version where it was working I understand.
take a look, forget about var definition. see if you agree (others welcome too)

 lcd.setCursor(x, 1); // draw first (top) row Left
    if (peaks[x] == 0) {
      lcd.setCursor(x, 1);
      lcd.print("_");  // empty
      lcd.setCursor(x, 0);
      lcd.print("_");  // empty
    }
    else {
    if (peaks[x]>8) {       //after value 8 you need to jump to next row, correct ?
     lcd.setCursor(x, 1);
     lcd.write(8);
     lcd.setCursor(x, 0);  
     lcd.write(peaks[x]-8);
    }
    else {       //if not bigger we only occupy 1 row, correct ?
     lcd.setCursor(x, 1); //position inferior row
     lcd.write(peaks[x]);
     lcd.setCursor(x, 0);  // position superior row
     lcd.print("_");  //empty 

    }
    }