My2cts...
a friend of mine has one and I just fiddled a bit with it and here`s some things that I found...
The anvil holder / quick release system had a ton of play in all directions and the anvil didn`t lay flat against the top wheel.
Also, (forgive me if you have the knowledge, I just see many who don`t) you need to understand how the E-wheel works. It is a hammer & anvil. You crush the sheetmetal between the wheels, making it thinner and therefor enlarge the surface, which results in a curve. It has little to nothing to do with bending into the radius of the anvil- wheel.
That said, you need a really really stiff frame. Thats where these cheap e-wheels lack imo. Ofcourse you can stiffen up the frame, and redo the quick release system for play. The price is still ok even for just a set of wheels.