Joe,

Be careful not to underestimate the amount of CM rejection you may need. A Mini-Circuits T1-1 transformer, for example, has around 1 pf interwinding capacitance.  That may produce less than 30 dB CM rejection. Similarly, chokes only generate a few k-ohms, at best, broadband and against the few hundred ohm source Z of many long cable/wire CM sources don't do a whole lot.  If one injects a signal between the LAN-side 'ground' on a Kiwi and the SMA ground on the other end, the unwanted coupling is only around 80 dB down at midband and not more than 100 dB een down at LF>  Considering the kinds of currents that may exist on longisy LAN or antenna cables, it may take a *lot* of rejection to stay below the Kiwi's -157 dBm/1-Hz (or so) noise floor.

I'd not suggest using the Kiwi decoder. It was compiled from a much older and less capable decoder and fed with the same signal does not produce as many successful decodes even if/when it can keep up with the volume of traffic.

Recording/decoding on a separate RPI connected via WiFi gets around the interference noise source problem.

There have been some comparisons of knock-off v 'normal' Kiwis and AFAIK, the knock offs don't seem to do any better and maybe not even as well for most uses. KA7OEI has written about  some of this on his blog. 

You may decide differently but for myself, I'm not inclined to give freeloaders, those trying to make profit with little or no return on others' efforts my support.  I understand, but don't know for sure, that there was even contention between a 2nd knock-off and the first.  I suspect you would get better support from a stock Kiwi, should you stay that way.