Now unfortunately this really isn’t quite a simple as running some PCIE extender cables — nope. You’ll have to modify the BIOS first, which according to [Kamueone], isn’t that bad.
After removing the VL805 QFN package and soldering in the bridge PCB, [Zak] confirmed that everything was hooked up properly and attempted to use the Raspberry Pi 4 with a PCIe extender.