I think you're right Dan....BUT.....the Frog Vibramatic is quite different in its mechanism to reed valve operation-unlike the Elfins and the Taifuns-which pretty much copied the Cox 'annulus and tab' reed layout of the early Cox-and can definitely be described as reed valve. The Frog-if you read the engine test (url posted by fiery above)-and if you've ever had one apart-uses quite a different system-effectively a spring loaded valve sealing a double backplate plenum chamber. Yes the operation is similar to a reed valve in that it is sole determined by crankcase depression/compression-but different in that it does not reply on the flexible deformation of a thin metal or plastic reed element to open and close the induction tract.
I also note the engine test (which I've had for many years)[the Aeromodeller engine test, not the Model Aircraft one] mentions that the system did not work very well when applied to smaller engines-nor when the return spring was weaker than that fitted as standard.
It would be interesting-though of academic interest only-to see what would happen if you went the other way-applied it bigger engines....the Taifun Blizzard, Jena 2/2.5cc and Jasolka 2.5cc reed valves, for example.......

ChrisM
'ffkiwi'