Thanks for your reply.
will they support 5 or 6 cards with risers?
have you tried them with less powerful cards? Something that will work for 750ti's might not work for r9 7990's.
there's 3 limitations I can think of:
cpu max pcie lanes
mobo bios max pcie/gpu's
data limitation on the mobo's physical lanes.
I'm torn between small gpu rig builds and building a wild m.2/thunderbolt setup.
I honestly haven't even taken them out of the box. Got them on sale on Newegg (a little later when prices started to rise) and right after they shipped there was a thread that explained 7 cards would not work so I decided to not even bother. We can reach out to a few on that thread and ask, but from my understanding these are best used with only 4 cards, but are rock solid apparently.