In short, even a relatively small dollop of stocks seems to be enough to provide decent assurance against running through one's savings too soon, while ratcheting up one's stock exposure doesn't appear to add a whole lot of additional protection against outliving your nest egg.
But BMW designed its Gran Coupe with its own distinct take on the genre, with a relativelysmall greenhouse canted inward around the edges and dolloped on top of a wide, powerful base.