OK,
Now we have the "real story" to work with.
Looking back through your previous posts the AUX tank fixed parts were fitted by EC or someone else?
There is a "trim weight" kit that can/should be fitted in this case.........
The trim weights are fitted in the nose and in the rear of the fenestron structure.
(No they are not dynamic balance weights)
The trim weights are designed to be fitted/removed wihout special tools as required.
Granted there is an AUX tank for 135 and 145 but if you do the numbers and research, neither system is very practical.