Yes it has extra weights in the tail boom. Without it the C of G is too far fwd so 2 x 90kg guys up front and two lady pax means you are in trouble. With the battery moved back plus the lead = no problem.
The tail boom weights are not that heavy so don't affect pax capacity and only small fuel drop. Way out there at the back of the boom they have the desired effect through the arm not mass.
Mine is floated and empty weight is 1126kg, MTOW 1715kg so you do the math. She can hold 315kg fuel, 5 people and lots of luggage - just not all at the same time. Take the floats off = 36kg more payload!