I used to make lots of these frames-aluminum front triangle and chainstays with a carbon seatstay wishbone. The combo works to give a really racy frame a smoother ride. I have used this style of frame for most of the all-day rides I have done in the last ten years. I think the larger companies bailed on this style of frame because of the amount of labor involved . The carbon stay will be bonded in after the frame is heat treated and powdercoated.