Yes, aluminum flashing would be nicer than the foil. The foil that I use is almost as heavy as flashing material. It is the type that they sell in art supply stores, kind of in-between turkey roaster tray aluminum and flashing in thickness.
It looks like crap, but has worked well for me so far.
I almost used thin titanium sheet, but I didn't have a piece quite big enough.
I may do that in the near future though.