CR gives a weather report for Mt Macedon (june 2015) and that it's a given BR couldn't drive the Merc in those conditions. I'm skeptical of his denials of what could or could not be done. Was there mention of snow by the eye witness who saw a man standing beside a black Merc coupe near the site on the 29th June? BR only needed that hour of reasonably good weather conditions to drive in for cover, and carry the body to the location it was discovered.
A dampened well trodden track can be driven on in a car and will leave little splattering of mud and dirt.
I agree with poster's theories that the body could have been taken somewhere else before the discovery site but I wouldn't rule out the other because of CR's claims. JMO
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This photo was taken at Mount Macedon during a snowfall last August.
http://www.bendigoadvertiser.com.au/story/3978070/snow-forecast-for-ranges/