Thank you for your question. You can go to the folloing link and select the 8' option and place two orders for them. We will give you a connector so that you will be able to connect the two 8' hardware into one 16' hardware with 4 doors. Thanks!
[https://www.houzz.com/products/wheel-design-double-stainless-steel-sliding-barn-door-hardware-10-prvw-vr~81205886?lid=63583335[(https://www.houzz.com/products/wheel-design-double-stainless-steel-sliding-barn-door-hardware-10-prvw-vr~81205886?lid=63583335)

I don't think you understand what I am asking. I want two rails, side by side, to hold two doors each so that they will stack, two over two in the extra 6 ft. space, but cover, when side by side, the 9 ft. opening. They will be staggered, two on front rail and the other two on the back rail. So I think I need two long, 16' rods that will be installed side by side and then the 4, --- 2'5" wide (each), doors will stack two over two when in the 6' opening and then cover the 9' space when needed. Can your rods do this? Anne

Sorry we don't have bypass hardware for stainless steel hardware.