I agree it is a nuisance that the currently-available hood insulation pads are flat rather than die-cut to fit closely to the underhood cross-bracing. Seems to me a tool could be made to cut the reliefs, but it would be a big project.
I'm amazed that ancient battery came to life! Hope you took close, sharp pictures of the label on all sides, for later reproduction.
(Also, I think the case is hard rubber, not bakelite)