I installed Dynamat inside the doors, under the floor mat, back seat, and all around the trunk, and under the hood.
They work great!
In case you want to install them under the floor mat, be careful not to break your door sill plates. Most importantly, to follow the correct instructions to depower the air bags, before you remove the seats.
2014 Mustang V6 3.7L 6-spd manual, with MGW shifter, Airaid CAI, BBK shorty headers, Corsa Sport axle back, strut tower brace, JLT oil separator, GT500 differential cover, BG Synchro Shift II gear oil, Redline differential oil.