Ok, I'm going to get technical now, the OE decal that is applied before the body side moulding is fitted, fits over the holes that are punched out in the panel to take the moulding. On a 3door car, the decal came from factory in 3 sections per side, ie front wing, door, and rear 1/4 panel...
The vinyl was in fact, was white in colour, the black and red were then printed on... That's why when you see an old decal, it usually has white patches and edges where the print has been rubbed away by cleaning and polishing over the years
I've fitted loads of these over the years, and cannot recall anything with an aluminium backing..
Best way out, if you can't get hold of OE, is to get hold of some black 50mm satin black tape, and some satin red tape to duplicate the old..
Thom