So the U.2 connector is per Making Sense of Next-Gen SSDs this article is a "slightly modified" SFF-8643. I can't find a description of this "slight modification". Would SFF-8643 to SFF-8644 adapters work? In other words, is it possible to run PCI Express x4 via an PCIe-U.2 adapter followed by a SFF-8644 to SFF-8643 adapter and the other end another SFF-8644 to SFF-8643 adapter and then a U.2 to PCIe x4 slot? All of these adapters exist I am just wondering whether it would work.