Grungle replied:

Best bet would be to contact someone up on the Cape such as Bramwell Junction Roadhouse (start of the OTL) or Archer River Roadhouse.

I find that any rain a few days before can create havoc with the rivers and creeks but they all subside pretty quickly. We did it last year (2007) and there was quite a bit of rain during June although we had no problems. Mind you there was a couple 1 day ahead of us that could not do the OTL because of rain and Palm Creek was running 2-3 metres deep at the crossing. When we went through the next day, it was around half a metre.\

I think you will be fine in May.

Regards
David