That's going to be quite a big balloon. For big read expensive to fill and keep filled. When you say positioned, do you mean either side of a piece of string or like an airship?
To give you an idea, this airship that I am involved with has 5kg of spare lift.
thanks Gary that looks great, we are trying to setup an antenna on it to send/receive data, so we will need to control its position to guarantee we receive that data.
I started thinking of building and hybrid using the ballon to reduce weight and a multirotor (quad/octo) since drones have lots of issues with weight :/
well not a hybrid at all blimps can have as meany en-gens as you can trow at it most common one gas Nito or 2 electric motors.
I saw International rescue episode they had a ionized helium balloons and a copter underneath! the idea i love it looked really cool! the helium would create negative buoyancy and the craft would want to go straight up the engens are there to do the reverse and drag the craft back to earth ionized helium so the balloon can go hiyer altitudes without rupture. the drawback is huge balloon you need a 30 ft balloon tho carry DSL and full size gimbals and radio equipment . he copter would need to be able to tilt the arms upside down to land.
The IR episode the used a couple of 30 foot balloons to lift something the size of shipping container looks much like Russian container copter . If your serous I can source all the parts and supply all the parts if your seriously interested .
but I found a other proportion system that will work with a balloon as well !