How strong/fit are you and how big is yr car?
A dob is great if visual is your thing.
Bigger is better, but if bigger means you end up not taking it or not setting it up often, then it isn't better any more...
There are plenty of IIS'ers on the Gold Coast. I'd recommend getting a hands on with a big dob and see if it is really what you want. Everyone here is pretty helpful, I'm sure some locals will chime in