It would be an Amateur Built Experimental (AB(E)) with VH registration. RAAus is out as it's too heavy.
If you contact SAAA in your area, they will be able to fill you in on all the rules and regulations and assign a technical counsellor to oversee your project.
It should be straightforward as far as the rules and regulations are concerned, just a lot of time and effort to put it together, particularly if you decide to scratch build rather than buy the kit. The Wikipedia entry says the build time for a kit is 2,500 hours, which probably means that 3,500 to 4,000 will be more realistic.