I've seen quite a few Schwinn bikes over the years, but one of the frames I see least often happens to be one of the bikes I have-- a double curve bar frame. Does anyone have any history or information specifically relating to this particular type of frame? How common were they? I'm just curious because I've had an old Schwinn for awhile now, and the frame just seems different from the straight bars and DXs you often see. Was it that these bikes could not take a tank? Were they a lighter "roadster" type bike compared to the fully accessorized ones?