Sorry, wasn’t commenting on your post, more on the topic. As far as I know, the only time you could fly IFR without a clearance, is if you were unable to contact Centre for a clearance, whilst taxiing for take off at a Class G airfield. In that case you can contact them once airborne. They have your flight plan, so Centre should be aware, you will be calling them at some stage. The system of SAR flight following and traffic separation, all becomes ATC responsibility, under IFR. Another interesting one is an IFR Dash 8 arriving at a Class G airfield. If the weather is bad, an instrument approach is flown, and in bad weather, no VFR aircraft should be bashing around the circuit. But for a Dash 8 out at let’s say Moree, when descending to join the circuit, radar contact will be lost at some stage. All centre can say is they “have no reported traffic”. In good weather however, the Dash 8 will be speaking on the CTAF, for normal Class G circuit traffic procedures. My experience at Tamworth (after hours) Armidale and Dubbo for example, is, they come in pretty fast, preferably on a straight in final, and most people just extend upwind, downwind or orbit on downwind, traffic permitting, to get out of their way, in respect and understanding of every minute extra airtime, eats into the profit margin!