From the FAA Weightshift Control Aircraft Flying Handbook:
Weight and Loading
Weight and loading must be considered before each flight.
Do not exceed the maximum gross weight as specified in the pilot’s operating handbook (POH). The balance of the pilot, passenger, fuel, and baggage is usually not an issue, but must be reviewed in the POH for the specific make/model since some may have balance limitations. The fore and aft carriage attachment to the wing hang point must be within the limits as specified in the POH for weight and loading of the carriage.
Always follow the POH performance limitations.
From the ©AirBorne WindSports Pty. Ltd.: PILOT HANDBOOK - EDGE SERIES MICROLIGHTS
5 WEIGHT and BALANCE
This aircraft must only be flown solo from the front seat. No ballast is required if the pilot weight is above 65 kg. If the pilot weight is below 65 kg it may be necessary to carry ballast in water bags. Ensure the bags are watertight and safely secured in flight.
All aircraft operations may be carried out whilst solo, as when the aircraft is flown dual. With lighter aircraft AUW the full-power setting may have to be reduced to get a safe climb angle after lift off.
The wings have three attachment points on the universal bracket. The forward setting will increase the trim speed and the aft setting will decrease trim speed.
The variation of attachment point has been designed to allow the pilot to pre-select the centre of gravity position prior to flight.
Under normal operations the trike base should be attached to the wing in the middle position. The rearward trim position must be used with MTOW of 340kg or less. In flight the only noticeable difference is the control bar pitch pressure, which increases as the hang point is moved rearward.
The fuel capacity must always be considered when measuring the AUW of the aircraft. Remember that fuel is measured at 0.7 kg per litre and may slightly alter the aircraft’s performance during take off and landing.
You have to fly iaw the Manufacturer's Pilot Operating Handbook for the aircraft you fly.
Weighshift Aircraft may have a choice of hang-points although, as stated above, the middle position is normally used. In training you are advised not to move this position and later, only if you know what you are doing. Nevertheless, the CoG is self-correcting.... and all we have to calculate is AUW.
Note: the specific weight of fuel is more correct in this manual