Touch upâs should be done minimum 4-6 weeks post the initial treatment. This allows time for eyebrows to heal fully before perfecting them for the second time. Free touch-ups are only valid up to 3 months from initial procedure date.
Re: The Tinny sound? Most folks that are concerned about a tinny noise with aluminum boats are referring to the noise generated by the hull moving through the water (which can be modulated/reduced through many different avenues). You mention vibration and rpms, so I'm guessing that you're not referring to that sound.
Snare drums; Brass: A very sharp edge to the sound and very rich with mellow overtones. Steel: A step more towards bright with a very pronounced ring, allot of body and longer decay than brass. Aluminum: Clear, open sounds with bright, crisp overtones and is capable of incredibly loud rimshots. Bronze: A close cousin to brass with the overall character of woods, can be loud, a good all around drum.