For weighting the bottom of the trash cans, we have decided to use standard domestic automotive steel wheels, approximately 15" in diameter and weighing approximately 22 lbs.; teams wishing to duplicate this for one of their own trash cans can probably get used wheels for $5-10 (and auto supply stores will sometimes just give old ones away since they are often stored out back for scrap pick-up!)
The wheels will have their outer surface face downward so that the lowest CG is achieved.
The wheels will be secured to the bottom of the trash can with some wood shims, bolts and zip ties so that the weight does not shift around when the trash can is getting tipped.
The false bottom of the trash can is made from a round piece of 1/2" plywood that is mounted to the sides with wood screws. The top surface of the false bottom will be 14" above the bottom (lowest level) of the trash can.
This puts the top surface of the false bottom 13.5" below the rim of the can.