Just to test what would happen, I swapped the tiny SDR for the original long one from the first Stratux parts list. I had no issues receiving towers over 14 hours of flying. This is with the R-Pi 3 running the latest release as of a week ago. I don't see any diffference between the R-Pi 2 and the 3 in use. I did lose the Wi-Fi dongle, but had to install it in a plastic case instead of the metal one, but I did not notice any RFI as a result.
I did notice that the three devices I have running iFly would not all report "no heartbeat" at the same time. Sometimes the 720 and the Android phone had no heartbeat while the iPad reported "receiving" for a good 5 minutes.
The enroute weather was great, the traffic was a bother. I only once was able to see the other aircraft out of the hundreds reported (and I don;t have out - just what was sent to someone elses hockey puck.