A question about insulating for sound

I've done an insane amount of reading about insulating. I thought I had all my materials on hand for doing the floor but discovered today when reading a comment made somewhere by Orton that MLV worked best with a layer to isolate it from the metal so I ordered a roll of 1/8" polyethylene that I will apply as the layer under the MLV I already have.

Later I was gratified to see when I re-read the sounddeadener website that was specifically what they recommended doing.

The only person who I've run across who describes going to the effort to sound deaden the driver's compartment is KLP in his impressive "Yellow bird" write-up.

Now I feel compelled to follow his footsteps and it has me worried because even he hasn't yet described overcoming the challenges of insulating all of that nasty area with it's potential for setting off airbags and whatever other threats exist there.

It has me wondering how many on this forum who have described extensively their insulating method have thoroughly tackled doing the driver's area? Do you do the firewall, under the seats, do the seats have to be removed? Do people insulate their driver and passenger doors? Do you use CLD and MLV?