at a later date during reassembly of 2511 after the collision damage, I fully covered the roof of the cabin with Dynamat
getting anything to stick to the roof will require time, patience and a lot of drop cloths as you remove the remnants of the OEM foam-backed headliner material
after mechanically cleaning the roof you will then want to use a solvent to remove remnants of the OEM foam and adhesive
like others, I had concerns about the Dynamat losing adhesion due to the exposure to full sunlight heat
Prior to installing the Dynamat to the roof I used my heat gun to warm the Dynamat and also to warm the roof, figuring the heat would improve adhesion
I spent considerable time using a roller to firmly press each piece in place prior to installing the next piece
I chose a foam backed modern headliner material to replace the OEM headliner, and used 3M spray adhesive to attach it to the Dynamat
this was probably two years ago, car has spent many hours at shows and on the road in full California sunlight and there is no evidence of sagging anywhere on the headliner
As for the Dynamat on the doors I used a 12“ x 24“ piece, cut in half for better manageability. Again I used my heat gun to improve adhesion and I have had no signs of anything loosening
Larry