Please do, if you find that convo a thread in the Networking forum would be awesome. Have you tried actual Mellanox FDR cables? I couldn't get any of mine to link at FDR speeds without paying the FDR cable tax.I am fairly sure it was cx3's and the cards where working fine with the exception that they didn't want to link up at 56GB/s and needed 40 instead.
Would have to look my old conversations to get details if you are interested. I think i might even be running some of the converted cards somewhere, would need to check psid's