A post I made today on a new platform I'm testing out. This maximizes endurance at the cost of agility (aggressive flying) and weight lifting. You can go as far as you want, but I chose my limits at 500g max payload. Flying a hexa up to 200g is a very good limit for max endurance and its got enough motors to load some more battery power. 200g payload can go up to 53 minutes flight time with 2 bats or probably about 38-42mins flight time on a single (battery dead). In this video I discharged the battery to nominal voltage from full in 30:30 and I wish I could take it down to 3.4V to see where that would end. A quad is 4 minutes more efficient, so you should expect to get 50minutes flight time on a single battery with some fpv gear no gopro.

http://www.diydrones.com/profiles/bl...ce-multirotors

Secret sauce is in the battery. You want a lot of capacity with little weight. Here in use is a maxamps 11Ah/4S at 852g. It's hooked up to 6x 15/5.5 props with 360kV motors. Next is the simplicity of the frame. It's not about rigidity or sturdiness, but low weight and "strong enough". So a couple of plastics, 1cm alu tubes and a clever method to put it together.