Are EZ Gains disc covers just as good as a disc wheel?

In this video I catch up with Clint Butcher who is the brains behind EZ Gains. EZ Gains is a company specialising in aerodynamic components for your TT/triathlon bike without breaking the bank.
I wanted to know if these components work, and if so, by. how much? So I tested everything Clint had to offer on a 11km TT circuit (out and back) in Mallorca. Although this may not be the stringent of testing environments the results did surprise me. Wait until the end of the film to hear the results.
EZ Gains state that the following gains to be made from their products.
Disc cover - 10 to 15 watts
Front Derailleur Guard save 2-5.8 Watts
EZ Aero Chainring Guard save 3-5 Watt
Aero Compression Calf Guards 5.5 Watts
With a possible saving of - 20 - 33 watts
Website here ezgains.co.uk/en-esp
This film also shows you how easy and quick it os to fit and EZ Gains disc cover.