How to decide values for grain properties?

Hello LIGGGHTS forum,

I am still confused about deciding proper grain kinematics for my simulation. Could I get some help?

I am using three different types of particles with radius 0.03, 0.02 and 0.01 (in si unit) for a drum like sagmil simulation (for test simulation only).
Currently I am defining poision ratio = 0.3, cofficient of restiturion=0.6, sliding friction = 0.2, rolling friction = 0.1.
Density of grain is 2500 kg/m3, fillmass = 120 kg.

I am defining fill parameters as follow: fill time = 5 sec, total rotating time = 100 sec, time for 1 rotaion i s5 sec.

timestep = 0.00001 second (Each iteration step).

My question are

1) Are these parameter correct for simulation.
2) How do I decide proper parameters for different size of grains?

Thank you.