Hey! Just leaving this note as a point of
reference in case you decide to set up masses yourself:

The [plc_blocks.json] file contains a simple example. To explain it-
[
  {
    "block": "neepmeat:plc", - the block ID
    "mass": 500.0, - the mass, in kilograms
    "friction": 0.5, - the friction value against other surfaces
    "elasticity": 0.0 - the laxness of collision, should not be used for hard blocks
  },
]