according to my data, 820g extra weight will cause 5.9mah/sec, total 14000mah can fly about 39min, but motor rpm will be 9100-9200 when hover and cause overheat
my opinion is not more than 300g, so motor rpm will be about 7000, cause 3.7mah/sec
for 30min flight time with extra 300g, you will...