New Project using Phantom 3

[thunderbird]

with Phantom 4 up to 600 grams is ok, I don't dare to do more than 600 grams for P4 but again the more weight you carry the more juice it takes, As for P3 It can go more than 600 grams, I know someone who did a battery mod on P3 to carry more weight for delivery and it goes well, If you Intend to keep less than 600 grams I would recommend to go with P3, Remember carrying a heavy Payload you need a reliable mechanism that will be able to release it, A servo Spec require Min 4.8V - 6V to provide a sufficient Torque for the release, Running on less than 4V might works during test but might fail to release during In flight

5V Release Mechanism Phantom 3 & 4 All Version Payload Release (Black Version)

 

[Neon Euc]

My recent test suggest that you will be alright

 

[Terry Evans]

Sir, I enjoyed your post. You have so much about drones to learn. Do a search and see if you have a DJI store near you. I have one within 30 miles, and it is enjoyable to go in. They offer training and repair work, too.
Good luck.
Terry