How to set the weight of different particles reasonably by MFIX-PIC method?

Dear all,
I want to use the MFIX-PIC method to simulate the flow of binary particles in the fluidized bed, in which the volume ratio of particles is 1:1, the particle size ratio is 1:6, and the density ratio is 2:1. I want to know how to set the weight of two kinds of particles to ensure the calculation accuracy and reduce the calculation loss?
Thank you!