Great post, happy to see someone do tests like this -- I've been thinking about it but am not sure about how it could be funded.
A couple of questions just to clarify. The UBNT gear you were using was all rather recent, and (I follow FCC approvals pretty closely) the PBE was only approved for very low power once you upgrade it to DFS. Not just low power onDFS, but low power above 5.725 too. Its 5.15 approval is very low. The smaller NBE is approved for much higher EIRP. So did you record and compare transmitter power levels between those and the ePMP? The Force 180 doesn't even seem to have FCC approvals yet -- I assume you were testing a beta under Cambium's experimental authorization. So we don't know what power it will be approved for. (It is a crap shoot, almost literally, under current testing procedures. A change to procedures is being discussed with the FCC.) The older ePMPs are approved for decent power levels (old tests).
Also, did you test on any cluttered paths -- trees in the way? The 5 GHz band isn't really good there, but sometimes you have enough signal to blast through a few.
BTW it's "line of sight", not "site", but it's a common error. ;-)