I have set up my Flex 6600 to use WSJT-X->HRD->SmartSDR Cat (CAT, Serial, FlexVSP, COM5). It seems to work fine except on 40 meters. On 40 meters, when transmitting, network packets are dropped and sometimes they are dropped to the point of losing communication and I've seen SmartSDR terminate. I'm guessing there is interference on the Ethernet cable that is only problematic at around 40m. I did switch to using the CAT 6 cable included with the 6600, but the problem persists.