Clare Rusbridge has a CM/SM breeding guideline summary for all relevant toy breeds on her website http://www.veterinary-neurologist.co...y_download.pdf
Looking at the little bitch in the certificate shown above, these guidelines suggest that the safest mating ( as far as the resulting puppies are concerned ) is to a scanned male with no SM or a dog over 5 years old with central canal dilation (CCD)
The guideline does not try and address CM. Ideally one would want to find a mate that fits into the above criteria and also has no or very slight CM, but that possibility is very remote. The vast majority of Cavaliers will also have a 2 grade for CM.
It appears from some recent comments that some breeders are not aware that this guideline to the new Scheme exists. They are expressing concern that people will breed from cavaliers in pain that have scans that show no SM.
This guideline clearly shows that dogs that are symptomatic, with clinical signs of CM and/or SM, are in the red 'Do Not Breed' section.
Advice from Specialists has always been that no symptomatic dog should be used for breeding irrespective of how well they scan.
Cavaliers......Tommy Tuppence 2000-2012 and a half share of Faith.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.