Adding fuel to the EC120 doesn't really make any difference to the CofG position as the tanks are pretty much inline with the main rotor. You will find you problem will be forward CofG limits.
We fly with 5 x 13 stone people on a regular basis and add fuel and cargo to bring the aircraft to MAUM. You can get a little bit more weight in the cabin, but not much. I fly a pretty basic EC120, no addititional equipment installed.
It depends what you are planning to use the machine for, it's great for a private owner blasting around the countryside with a couple of pax, trying to get a good cockpit load and a couple of hours fuel may be tricky. If so, buy an AS350.
Just some thoughts, TiP
