Hi phendry
We have done some tests using 5GHz-only-N. As far as I know you can not use N-streme in conjunction with -only-N.
Up to 8km link we have reletevely stabe performence using R52N both ends. We then set up a 29km link and experienced exactly the same problem as you describe. As soon as you load the link the quality deteriorates and the link collapses.
What is interestesting is that we are also testing a Ubiquity rocket on a 22km link which also uses N protocol and have had stunning results - 95Mbps throughput, full duplex and quality is excelent.
Ofcourse we had to put rb433 on eather end to do the testing as Ubiquity’s setup and features suck! Oh how i wish Mikrotik could deliver this performance as I want to stick to Mikrotik only on my network.