UPDATE: ok, so this is interesting. This morning I was playing around with my primary DVR and Remote DVR is WORKING, despite still being on a 2 router setup (LAN to LAN from the FAQ)
I did enter port forward rules for 4567, 63145 and 35000 ... even the Caller ID test I did from the box worked.
This is awesome, question is how long can I keep it operational...
Here's the way I have my rules setup in the primary router (RT-AC68U w/ Merlin build)