It was basically to keep costs down by using the donor seats, rather than buy buckets, and just for a bit of comfort space. The only reason why I say this, is a few weeks ago I had a tour around gbs. They had a normal bodied gbs zero, which fitted snugly, and a wide bodied gbs, which felt a little more comfy once inside. As my wife says, a few inches, makes a huge difference ! Lol
