Viewing craft and sewing rooms is so inspiring. There are so many good ideas to be absorbed. Because there are many users of the light weight, drawer systems, I thought I'd share my experiences and solutions.
1) Forget the casters. When adding weight to the drawers, the casters buckle in their sockets, causing a bow-leg effect. This prevents rolling, tilting, and even fall overs. Solution options: a) do nothing. Just let the drawers sit on the floor with no base. They are stable, and nothing, including dust bunnies, gets under them. b) substitute a rolling base by cutting a board the side of the drawer base, with a 1/4" border. Drill holes an appropriate size to accommodate the casters which came with the drawer unit, or use your favorite decorator casters from your local hardware store. 3) Not handy with tools? Pick up some of those wooden plant casters from the local discount store, and put one under each side of the drawer unit. This will help support the full drawer, not just the corners. And, with eight wheels, cat toys and spools of thread become more of a challenge to retrieve.
2) Stacking - The challenge is how high can we stack, and still reach the contents? When stacking, the upper unit tends to slide off of the lower unit. Solution: a) This is often resolved by using an anti-slip mat cut to size. b) However, (assuming you have the identical set of drawers,) a better solution is to remove the top of the base and set the second, or third set on the frame of the lower set. With drawers out of the frame, carefully note the construction of the frame at the attachment point. Most drawer units have a pop-out which prevents the drawers from inadvertently dissembling. Apply pressure to the pop-out, pushing it into the frame, freeing it from holding the top in place. Some units are more difficult than others. I've had to use a standard screwdriver to get leverage on some of those rascals. (Save the liquid one for later.) Once each corner is loosened, the top should pop of easily. Stack the next set of drawers on the exposed frame and press each corner until it pops into place.
Place the frame in its new home, insert the drawers, fill 'em up, and get that (liquid) screw driver while you admire your handy work.