The idea is to glue it to the lower side of the hood of my car to reduce the noise coming out of it. Some more will be applied between engine bay and feet area, to reduce the transmission on that path too.
How to glue that kind of panels to the painted metal? Is silicon ok? (the one applied with a gun) I know there are various types. I have a tube barely used for my bathroom, and it will dry out if not used, it would a good way to use it.
Or is Bostik glue (yellow, sticky, elastic also when dry) suitable? I would not use single points but spread a sort of spiral of glue on the panel and then keep it pressed for a while on the hood.
Should I add also some additional structure (thin wooden frame) to retain the panel for increased safety? The panel is quite light per unit of area, so the vertical force is not relevant, but to be sure...
What if I apply to the hood some bitumen/aluminium foil strips to dampen vibrations too? How to stick the dense foam panel to aluminium (or whatever it is) foil?
I also thought about using pins sticking through the panel (the part sticking out bent appropriately) and having on the other side a small plate that I can glue to the hood. https://www.gamma.nl/assortiment/isolatie-bevestigingspennen-zelfklevend-zink-10-stuks/p/B194520
Concerning safety and heat resistance: in the appendices of this study (on 3x as powerful cars as mine) it is shown that the hood never reaches 100°C unless idling for several minutes and at higher RPM than minimum. I will test the foam in the oven to be sure. Also, my mechanic suggested me a similar solution. In any case, if this foam appears not to be suitable, I can use sound absorbing foam, with a better fire safety rating. The question above still applies.
Concerning space: this is a 20+ old car, there is enough space below the hood and also the panel is not thicker than the metal bars already attached to the hood to strengthen it against flexing and torsion.