Powering a heavy modified 1921g Yuneec Q500


I have recently modified my stock Yuneec Q500 4K to hold a
6800 lumen flashlight. I accomplished this by adding longer legs and hanging
the flashlight at the center of gravity below the body on a strut that goes
between the legs. The light sits far enough below the gimbal and camera that
the camera does not throw a shadow on the scene being photographed. The drone
operates well, but as you might imagine is relatively sluggish compared to a stock
Q500. The original Q500 weighs 1284 grams. The modified drone holding the
flashlight weighs 1912 grams. This is an increase of total flight weight of
about 50%.

I am trying to understand the strain I am putting on the flight
controller, motors, ESC and the battery. When I fly the modified Q500 the
battery goes down to its LAND NOW voltage of 10.7 v in about 1/3 the time, 4-5
rather than 17 minutes. Interestingly, if I remove the flashlight, which weighs
557 grams (the additional difference in the weight is because of the longer
legs and flashlight attachment), the same battery that was just showing 10.7v
now reads 11v and allows me to fly the Q500 for additional time. I assume the
new weight is drawing more current from the battery and the drone controller is
reading that the battery is approaching its limit so it warns me to land. But I
don’t really understand what the jump back up to a higher voltage means when I remove the
flashlight. I am using the standard 5,000mA 3 cell Yuneec battery.

While Yuneec does not seem to publish data related to its
motors and escapes, I see from the internet (https://www.youtube.com/watch?v=nJJxdgVihvY)
that the high? thrust of a single motor on the Q500 is 1468 grams, at a current
of 21.91A and a Voltage of 11.47V and a wattage of about 265. These tests were
performed with a 2,000mA 2S battery. At a low or medium hover? speed the motor
seems to have a thrust of 475g at a 3.72A current, Voltage 12.12, Wattage
45.12. To fly my Q500 with the flashlight load I do not seem to have the sticks
in unusual positions, the drone just moves more slowly.

Based on the 1284 stock weight I would assume I would
ideally need 2.2x grams of thrust or 706grams in each motor at medium hover
speed. The current motors seem to have about ½ that capacity. This seems to
make sense since I must be driving them at twice their normal hover speed to
get the thrust needed.

Questions: Is the faster discharge of the battery just due
to weight or are their other issues? Am I over discharging the battery? Will
that damage, or how soon will that damage, the battery, the esc, the motors as
well as the flight controller?

I see that Yuneec does make a prop, the Aeronaut
Propeller, which has been calculated specifically for higher thrust even at low
speeds . (It seems to have been designed
for flights from higher elevations, ie 8,000 feet.) To achieve this, a thin
profile with greater depth was used with this series a lightweight, stable and
rigid, Carbon reinforced propeller. Would this help?

Any comments or suggestions would be
appreciated. I understand that if I continue to want to attach heavy gear to
the drone, I will probably have to build a more powerful machine.