Recently we showed you images of BMW's apparent replacement for the 3 Series coupe -- a '4 Series' two-door -- so our spy photographers braved Europe's freeze to follow up with shots of the convertible version. Parked in the snow and wearing BMW's now-ubiquitous efforts in disguise, the wide and low two-door has a rather awkward-looking rear end -- a characteristic of most coupe-to-convertible models packing a metal roof into boot space. Soft-tops generally have a better profile, due to the compactness of fabric. There's also some heritage with the 3 Series convertible and fabric roof; maintained for savings in weight to align with BMW's performance ethic. Presumably the introduction of the all-new 4 Series range will allow BMW to break the mould and apply a metal drop top to its smaller and more affordable offerings. The Z4 convertible already uses a folding metal roof, to great effect...