Hi , I also bought the XG-C100C and it worked with bootloader 1.02b (DS3615XS) DSM 6.1.7 with the extra.lzma pack 4.9
I can't get it running on bootloader 1.03b (DS3617XS or DS3615XS) DSM6.2.... , for now I'm using the 2 onboard 1Gb lan ports and created a bond (Load ballance)
Lan speed will remain 1Gb but it can handle more traffic from separete sources , can't wait for an extra pack for my configuration so I can use the 10Gb card.
Still learning and trying.