Hello again folks and thanks for your feedback,
I've made the changes this weekend:
with no consumer's traffic i was able to pass 500k/500k pretty stable, as is.
then, i've enabled Nstream: 1.4M/1.4M, a bit more and it began woking erratic, in the same way it did at 600K without Nstream. so, no way to achieve 3M/3M or close, like I said earlier, no great improvements.
I insist with 3M/3M because I take another ~25Km link as reference, but no mk gear just senao and IEE 802.11, and it cost 20% of Mk,
Nstream discused many times but no conclusive answers, at least for me... maybe a little more extensive documentation would help...
RG213: true, but LMR400 is pritty hard to get here, I will try to change it at the first chance.
I will change both radios, and try again this week...