We've had many discussions with Fred on this issue and I think you'll find that they are pretty rigid in their interpretation of the standards document where it says
2.2.7 Radio navigation equipment should be installed including at least one VOR or ADF receiver
Fred's view is that installed means more than stuck on with a piece of gaffer tape. That's just a view and the standards document isn't law though, so you're welcome to challenge it, but everyone else just rolled over so be prepared.