I had one (trolley) professionally made, and a mate bought one which is the ducks guts.
Mine is pretty light, but my mates is very very heavy.

The higher the pinball machine is lifted up on any trolley (and the lighter the trolley is), it makes it more unstable for a very heavy pinball.

** An example, is like having the worlds lightest forklift lifting heavy objects. If the forklift is too light, it falls over with a heavy load on it espescially as the heavy object is lifted higher.

Its a catch 22.