Yup. The daughterboard is on my mind. Likely flex-PCB and that’s gonna take a week or two to respin. Hence I’m collecting ideas for various daughtercards I could cram in a panel before sending it off - straight-through to riser via USB3, expresscard SMT, maybe through-hole 1x?

That said, PCIe phy’s are extremely robust - they do most of the impedance matching and delay mismatch training. And if you don’t ruin the onboard caps, this could be jumpered straight across.