Covering those holes is a must. It will help bass response alot.
Most of those contours dont look that deep, no need to use such small pieces. The more you practice, the larger a piece you'll find you can lay out and not get any tears or bulges.
The aluminum does not stretch, its not like the old asphalt stuff you could just heat up and stretch any which way you wanted. So with crevices, you lay the mat a bit at a time, using your fingers to mold down into any of those depressions, working from one side to the other. The trick is not just trying to stick the whole piece up all at the same time.
The larger the pieces you can lay at one time, the faster the project will go. Those door pics look rather time consuming for an area I would have done in 1-3 pieces (inner skin).