M20E,
Its nothing to do with safety. The regulation prohibiting carriage of goods for trade on a private flight comes from the CARs, not the CASRs.
If you can get your tools to the destination by means unrelated to aviation, good on you - and the Civil Aviation Regulations don't apply. But if you aviate your tools up there for the purposes of trade, then you need to ensure compliance with the CARs.
Whether it sounds logical or not, its not permitted under the category of a private flight.