Just to be clear you had the longest flight with the *stock* controller?
I personally haven't found the limits of the stock or modified remotes. My issue is always battery.
However I just got 4 4.0 MS's and 2 5.2 MS's. I'm hoping for better results.
For some reason when I try to do two 3.0's I get a weird error.
At some point I'm going to push both of them their edge by doing a 1 way flight!