To my knowledge the side exiting pipes are still illegal in QLD for new Cobras, but in SA there was a recent post:
Working side pipes now legal in South Australia
Also, the way you are going at it seems fine, to me at least. Deciding, after registration, to remove the rear routing and exit in front of the rear tyres, is up to you, the local cops and your insurance company (they will always look for an 'out' in the case of an accident), however.
Very few of us have done that, as the cars do attract a lot of attention, but the rules may change in QLD at some stage.
Keep us posted. The Harrison is a pretty good product. Did you get the extended body?