Look Editor I have great respect for you knowledge about Inspire 1, and SUAS in general - but in this case your are wrong in many difference ways.
1. The numbers and calculation you make does't work like that in real life. For example the motor max output is a bench test, with no limet on what amount of juice you can pull from the battery. In real life a motor can not deliver more power that the battery can deliver - Take Tesla p85d they just changede the power output form around 700 HK to 539 hk. The 2 motors may deliver 700 hk but the batteries kan not deliver enough amps so the real life power output is much lover.
2. I know you know all about how a inspire1 works. For other that may read this, you increases or decreases the power on diffrent motors to steer it. You need to have some power reserve to be abel to control the inspire1. That power reserve is rather big. For the E800 propulsion DJI recommend a takeoff weight of 800g/motor. 4 x 800= 3200 g. That means that at around 3200 g is it safe to fly. You can push the envelop a bit more, and still maintain good control - but as both tcchow and I report it is getting very hard to control when the weight come close to 4000 g.
3. Try look at this video. The inspire is without the kamera and wights therefore around 2.719 g (2935 - 216) and a payload of 1967 g = 4.686 g. Try see how difficult it is for him to controle it. And you will add 1.532 g and say it could fly because that is what is calculated ind your ops manual ?
4. What 3dpico in fact asked about was if he could pace a rig with a weight around 2 kg and with a TB 48 get 9-10 min flying time in moderate wind (10 mph gust) The wight of inspire 1 with out camera but with TB48 is 2819 g. payload 2000 g = 4.819 g. He might make it take off (if the rig has som distance so the downforce from props don't make it heavier) but it will be very hard to controle, and flying time will hardly exceed 4-5 min. flying time.
5. Talk is cheep as you say. I will (hopefully) tomorrow make a test with a scale a give you an exact number on what the maximum take off weight is for the inspire1. (the number will not be the same as a payload that is controllably to fly with but never the less.....