guys, im going to give you a little idea of HOW buytl+aluminum CLD tiles work.
there are three things in constrained layer dampening;
mass to be dampened (sheetmetal in a car)
constraining layer (byutl rubber)
reflection dampening layer (aluminum)
basically when the mass to be dampened (hencforth sheetmetal) is vibrating, it will ring until the energy is either lost in heat, or radiated into the surrounding air as kinetik energy. this is bad for us. vibrations from the car driving along the road, from the air wooshing past the panels, from the engine turning - all these can excite the atoms in the sheetmetal and make it reverbirate.
so what do we do? we need to counter the ring with an equal but opposite force as best we can.
so, we develop a constraining layer (byutl hencforth) to bond a reflecting dampening mass (aluminum henceforth) to the sheetmetal that will respond to a vibration with an opposite vibration, canceling out the first vibration.
an anology would be thus, if you were jumping on a trampoliene (the trampoliene being the sheetmetal, and you being the vibration) we could add a SECOND person (a reaction vibration) to the mix that will land as soon as you bounce - stopping both bounces and making you both fall down mosty likely. most of us have expierenced this.
in order to DO this, we use the first vibration impact to push the aluminum layer at a delay that coencides with its distance from the sheetmetal. this first impact causes the aluminum to vibrate 180* out of phase with the sheetmetal, hopefully causing both of their vibrations to stop dead in their tracks - or close to it. it is a passive system. so the viscosity or rubberness (however you want to describe the buyul) and its thickness are very important to get the aluminum layer to vibrate at the right phase-time to the sheet metal.
if those factors are not right - then the cancelation wont occur as best as we would like it, and the sound dampening wont work very well.
considering that the flashing tape is designed to be water\heat-resistant sealant, i wouldnt guess that the chemical composition of the byutl would be very good compared to specifically designed sound deadener.
TL-DR - do yourself a favor, and just cover 50% of the sheet metal you are concerned about vibrations with good CLD tiles.
check out
Welcome to Sound Deadener Showdown | Sound Deadener Showdown - they have VERY informative explinations of their products, even if ordering them would be cost prohibitive, its worth a read through.