Folks,
Sadly, Murray Cod's experience is SOP with CASA, as is the advice to get an FAA STC.
I could (but I won't) quote the experience of a number of small and innovative Australian companies that have gone down the FAA (not EASA) route, CASA being impossible, timescales quoted in years, not months, not to mention the scale of CASA charges sending you broke.
Another benefit of the FAA route, a commercial imperative, is that quite a few national authorities will not recognise a CASA STC, largely because these national authorities do not regard CASA as competent, probably quite a reasonable assessment.
Even with the US/AU bi-lateral airworthiness agreement, a CASA STC is not a given to be accepted in the US, and good old CASA will even put roadblocks in the way of that, even if you do get a CASA STC.
An FAA production certificate will also be easier to arrange/maintain.
Tootle pip!!