I used Peel 'n Seal in my doors, roof, and floor when I built my '56 over 10 years ago and have had the same positive results noted above and we get at least as hot as Colorado here in eastern Nebraska. It's a very good alternative to the expensive stuff. I'd do it again in a flash.
I've got 10+ years daily driver only vehicle, I paid $16/roll works great, if you want to spend money on some company's advertising budget they will accept your checks.
I used a 6" horizontal piece the width of my doors and it took out all the 'oil-canning sound', did the entire floor and ceiling, quieter, I know it's warmer in winter.
