I used this Dyno-Mat-like sound deadener on the floor boards and behind the seat on my AD. I just put ONE horizontal 6" X Width of door strip via accessing the five-screw bottom access panel. The product has a protective backing that you peel off, the product itself is self-adhesive. What a difference! The 'door echo' has been eliminated completely!

I believe this product comes in 6" and 12" widths, available in the roofing section of big box hardware stores. For 25-30 bucks you can do most of your cab. In fact I believe I read here or elsewhere that 100% coverage is not necessary for sound deadening purposes.

~ Cosmo
1949 Chevy Half Ton
Rocinante, like Don Quixote, he is awkward, past his prime, and engaged in a task beyond his capacities.
"...my good horse Rocinante, mine eternal and inseparable companion in all my journeys and courses." ...Don Quixote, Cervantes
"If you come to a fork in the road, take it."...Yogi Berra
"Rudeness is the weak man's imitation of strength." ...Eric Hoffer