Does anyone have experience of doing agility with giant breeds? I would love to start my eight month old girl but the breed doesn't reach full maturity until they are two, She has no health issues but, as a breed, they are prone to skeletal issues and I wonder whether it would put too much stress on her joints. Would love to hear from anyone who does agility with St Bernards, Bernese Mountain Dogs, Nerfoundlands, Tibetan Mastiffs or any of the other chunkier giants what age their started their dogs at and tips for avoiding injuries