So how about posting your new flightimes? Im thinking about this mod myself but, only if it warrants 30mins+ of total time.
I have a set of MultiStar 3000mah 3s LIHV batteries. I did a test with only 1 of the batteries (3.62 miles out and 3.62 miles back 7.2 miles round trip, again this was only 1 battery not 2) and AirData reports that I had enough power for 28min. I landed back at takeoff point with 40% batteries left in the tank. I will also say that the height was at 700ft and was getting about 10mph wind from all angles (out and back). A second flight at only 6 miles (round trip) reported 29.5min. So most of the heavy wind on the first flight was out past the 3 mile mark above 600ft.
I will plug both batteries in on the next test, I want to do 4.5 or even 5 miles out. I just got back from flying today but it was to windy for a distance flight so I just flew in the mountains.
I should mention too that where I fly at the elevation increases dramatically so I am in a constant climb to keep above the ground.
I also have 2x turnigy 1000mah and 2x zippy 1300mah batteries that I am flying with. Believe it or not I went out 3 miles with the 2x 1000mah batteries and came back after 14min45sec with 50% still left on the Mavic battery (AirData reports 29min16sec).
I think it has to do with perfect conditions, location and the weight of the batteries. I believe that where I fly an additional 6 to 8 minutes of flight time can be achieved, if not more with the right battery setup. I haven't tested the 2x MS 3000 LIHV batteries together yet but I'm hoping to get 30+ min with them!