Any value of material density smaller than 0.09 g/cm3 (90 kg/m3) is ignored.
It is possible to enter there smaller number, but it still counts as it is 0.09.
For example, Polystyrene has 30 kg/m3.
It is a possibility to workaround by “Raise mass to Power”, but I want to have a solid piece.
I tested it on UE5.0.3 and UE 5.1
UE5.0.3 is even worse because there mass evaluation doesn’t work at all.
UE 5.1 is luckily fixed already.