You seem confident in your ideas, so why not go for it?
AFAIK, constrained layer damper solutions need to use a constraining layer that's able to handle the dissimilarity change and resist shear forces. Not sure how roofing rubber can handle that compared to aluminum foil which is very strong horizontally (along it's length).
One thing I always think about when it comes to DIY noise and vibration control ideas is if the idea is so great, why hasn't a company in the business used it already? Why hasn't Dynamat rebadged pails of elastomeric roofing compound, called it Elasto-damp Xtreme and marked it up 17,000%??? If there are engineers out there developing the best of these products, why isn't it already being done. Just something I think about, but it's never stopped me from trying as I've come up with some pretty nutty, off the wall ****.
