I hate bitumen/rubber/soundproofing mats that are self adesive, eventually they all crack, if strangely shaped surface you will not get it flat to the surface, there will be gaps, moist behind then = rust, they are heavy and there will be edges and gaps.
Now, enough complaining, I have started to test a soundproofing/vibration dampening paint and I must say I like it.
Used a spraygun for undercoating, still wet here:
It needs another layer, only one here, but now Everything is covered, with mats only parts get covered.
There are more pictures of this here: