JW arrival in Sydney

Listening to the last couple of episodes I'm confused by the way Jon's movements in Sydney have been reported on...not sure if I've missed something.

It first seemed that he had a good few hours alone that were unaccounted for so would have had plenty of time to be at the building site - we were told that the car wasn't registered for 2 weeks (that he lied about this)

But it was confirmed in the podcast that he actually did register the car on the day he arrived! Also in the ex wife & her mother in law's statements it seems the kids were only at their house for a couple of hours.

Though he did arrive to Andy's in the afternoon.. seems it was only about 2 hours in the morning where he didn't have the kids..so he registered the car at this stage or was at the house for the concrete pour?

The info given isn't very clear - very frustrating - but seems like a bit of a stretch that he had time to dispose of a body during this much shorter window?