Yes Doug I don't think they threw the old ones away! Not until the DTs were coming in in numbers in 1929-30, anyway. I've mentioned before that the "sloping top frame tube" models appeared here in the first flush of RAs, but were not seen much later.
Time for a bit of sidecar action. This photo appeared in Old Bike Australia in 2011. The person who sent it in knew nothing about it.
The names on the board in the background - Disney, Finlay, Gough et al. - were well known in Victoria, so the photo was likely taken in Melbourne in the second half of the 1920s. I've had a quick look but can't be positive about the venue, but either the Motordrome or Aspendale. I'm also not sure who the Douglas rider is, but his mount is an RA, looking particularly sporty. Sidecar races were not the main drawcard at events in this period; in some meetings had no event for the sidecar men.