I operate a helicam based on a Robbe Futura .60 turning 710mm carbon blades. I don't know about the maximum payload but I lift 2,5 kg (5.5lb) with ease. My concern is not the how much the heli can lift but how much weight it can carry during autorotation because there is allways a small risk for motor flame out using an IC engine.

You have allready been given the Runryder address and that is a great source to knowledge in the helicam business. Go through the posts there and I'm sure you'll get yourself a proper heli instead of trying to build one.

I think that two rotor heads just make it more complicated and also you need to think of the induced drag that will be twice a regular heli, which means that you can not just "translate" the lift capacity of a regulare .60 size engine. And you will still need a gyro to control the yaw even if you use counter rotating rotors.

In my opinion this project will never leave your drawing table. Go out and buy a heli and have fun instead.

Just my 2 cents
/Christian (aka Helikalle on Runryder)

PS. Have a look at my homepage about helicam if you like. Yeah I know it's in Swedish but the pictures are international :-). www.helifoto.se