You really didn't do that by halves!
Did you use that underlay under the carpet in the whole car or just the boot? I could get my hands on a roll of carpet underlay very easily if it is worth doing
I put the underlay in the cabin and the boot, but I removed it from the boot when I did my new install back in December. The floor in the cabin feels really squishy due to the extra padding
I have no idea if it made an improvement... I went from having no rear seat in my car to completely deadening everything. I assume it would be absorbing some of the road noise through the floor.
I had the underlay spare so thought I might aswell make use of it.
StoneX your boot look about the same as mine in regards to the amount of sound deadener. When I put it on I layed it with my bare hands and then pressed it down with my palms and then rolled it, must of finished the day with a million foil cuts LOL.