Ha, I've actually had to get medieval on a computer motherboard relatively recently!
I had to fit a card that uses a 16x PCI-E card into a motherboard with only a 1x PCI-E slot available.
With a little bit of neat hacksaw work while trying not to slice through any motherboard tracks, I managed to saw a cutout in the back of the slot, so the card can overhang out of the back. Fortunately, there were no tall components etc behind it, and it merrily works away (albeit at 1x speed, which is all that's needed in this particular use case). Great success!