I drive a 2018 Honda Jazz. I'm quite tall and the driver’s seat does not extend far enough back for me to be comfortable while driving. There are brackets that can be purchased from the USA to increase legroom for my car, but is it legal in Australia to fiddle with the seating position in cars? Also it's still under factory warranty, will this affect that?
It should be ok, but to be sure I suggest you contact Vicroads who will be able to put you in touch with one of their approved engineers. In turn they will be able to tell you if you would be contravening an ADR. By modifying the car you will affect the factory warranty in those areas you change.