Agree with you South Aussie. Tim Day verified that none of the vehicles in the convoy are suspected to be traveling with the black Mercedes (last 2-3 min of video). The police are only interested in any interaction which may have taken place along the route, any suspicious activity and sightings of who might be traveling in the Mercedes. Following is a link to the police conference for anyone who may have missed it:
https://m.facebook.com/story.php?story_fbid=1577823332289797&id=214542541951223
My hypothesis is that Karen's body was placed somewhere near the burnt out restaurant first, where some of Karen's belongings were found, to allow BR enough time to return quickly back to Melbourne, and so as not to raise any suspicions. Then at a safer time, he and VR and possibly CR returned to find a place in Mt Macedon to bury the body, but found the soil too hard so they placed her between the two logs. MOO