Australia Post Free over $150

I'm using the Australia Post shipping plugin but want to give free shipping for orders over $150. This seems to be the only shipping plugin without a maximum price. Is there any way to do this?

By default you can't set a maximum weight for this shipping method.
To have this feature, you have to duplicate the plugin, in the duplicated version add a maximum price (you can see how it's made for the minimum price and adapt the code).

Then set a price for this method for a maximum price of 150$, and in the other one no fee and minimum price 150$

If you don't have the PHP skills, you can ask to a third developer or post a request in the commercial jobs section of this forum.