First, I want to assert at the outset that you guys are the experts, I have no meaningful experience with optimizing the Mavic (both setup and flight control) for maximizing range. So please don't hold back with any comments/criticism/your-a-complete-idiot responses to this post -- I can take it!
Now, that said, I got into this sort of thing with my Hubsan 501S. Never did any mods to add more battery, but I did some antenna mods to the controller to gain some distance.
Anyway, what I really wanted to discuss here is optimal speed/forward thrust. After many many flights trying to keep extending my record, flying the standard practice of out into the wind, return with a tailwind, I found that the most distance-efficient speed was quite a bit higher than the limited speed with GPS active.
The 501S is similar functionally to the Mavic in this respect: With GPS positioning on, speed is limited to about half the top speed with GPS disabled. It flies very much like ATTI mode on the Mavic when GPS is turned off. With GPS on, top speed is about 15mph, about 30 with it off. 501S has a 2200mAh battery.
My record is 3300m, just a hair over 2 miles. For the 501S and it'
s controller, this is pretty amazing.
However, I found that in order to do this, I need to fly OUT full throttle in no-GPS mode, as well as back. I simply can't get far enough in GPS mode -- it's moving too slow. IOW, at the GPS limited speed, too much of the power is going into hovering vs. forward movement.
Where exactly the sweet spot is in terms of speed I didn't rigorously test. It may be balls-out all the way in full-stick "sport mode" (not what they call it), or something a bit less than that. Don't know. But the same questions apply to the Mavic as well.
So, I'm thinking you guys can get farther by going faster on the way out than P mode max speed. What we need to do is characterize speed efficiency. What I can say with fair certainty is that doing the entire outward leg in P-GPS is almost certainly decreasing your possible max range.
I'm thinking of doing some controlled testing to compare current draw from the logs to incremented fixed speed tests, and see where the peak speed/amps spot occurs -- this is where we'll get the greatest distance.
Mathematically, that works out to the distance/charge rate, as both amps and speed are time-rate metrics -- d/t divided by C/t (C==coulombs, a measure of charge), which yields d/C. mAh can be converted to C, so figuring this from the telemetry logged is doable.
Of course, when trying to maximize range, you want to fly at the highest d/C speed.