Well, over 2 hours later, this heater box is ready for installation. I scraped all the old caulking off and added new 1/8" non-adhesive padding to the front AND back of the door. This glue dries QUICK. There really is limited margin for error. Not to mention: you either need to be a contortionist or have small hands. Next was 3M caulking strip along the edge where the core sits. And viola!