No one has ever tried, because it doesnt make a lot of sense. It might
work, it might fail miserably.
One concern is that adding 2 identical PCI cards of anything often doesnt work. I once made a crazy "budget SSD" based on a RAID array with >30 USB drives (company gifts) and since I didnt have enough hubs or bandwidth, I tried putting in 3 identical PCI to USB controllers I had laying around, and it just wouldnt work. Only 1 PCI card would work at a time, no matter what I tried, the other 2 werent seen.
This was both on windows and linux.
OT, but here is part of the setup: