I'll send pics once the setup is fixed. The model I got was this:
https://peine-braun.net/shop/index.php?route=product/product&path=65_59&product_id=54. This is the narrowest model, but there's no space for this either at the motherboard PCIE slot or at the GPU-side PCIE slot. So I plan to put another 5cm extension cable to have this card on the top GPU side, with Ethernet card connected facing down, and the other slot connected to the standard 30cm cable leading to the GPU a the bottom, through the standard route.
Aside from cramming one PCIE card on top of the GPU side and one on the bottom, you could use 2 low-profile devices, so both would have proper PCIE slots. I didn't find a bifurcation card that would fit, and many of the unbranded cards on eBay were reported not to work in some forum threads. Ameri-rack sells risers that could fit:
http://www.ameri-rack.com/ARC2-PELY423-C7_m.html, but they don't respond to requests, and you can't find the risers from online. C_Payne custom makes the designs and is active in forums, so maybe he could make one especially to fit the Dan case.