having problems in rotomoding a 28mm thickness tank

Hi, I am having problems in rotomoding a 28mm thickness tank.

the tank it is about 3m length by 0.5m diameter and we are trying 110 min cycle with 293C (560F).

Polyethylene with density 0.93 and 4 MFI.

The problem is uneven wall thickness like 20mm one side and 36mm the other side...

wondered if someone could give me any tips to improve.

Thank you very much.

Kind regards

Ricardo.