Ozbusdriver mentioned PJE at Nagambie - one of the few DZs where drops through cloud are legal. The current AIP words in ENR 5.5 were written before there were IFR aircraft dropping meatbombs - so as VFRs there was no real need for a clearance.
Now we have the potential for the drop aircraft to be IFR (read clearance required in E), and with the controller unable to tell where the cloud might be, it seems sensible to require a clearance to drop jumpers through an IFR level. No real sweat for the jump pilot, who will want the trafic info anyway - and saves him getting the clearance into the D below in some areas, because the contollers will need to co-ord the clearance for both lots of airspace - and can you imagine a Class C controller issuing the clearance to leave Class C if there is trafic in the underlying E or G (as there may be if E below C happens in the next round of "fine-tuning")
Point is, the jumpers do not have transponders and fall faster than would show up for a properly-equipped VFR aircraft, where the controller can see it descending through the IFR levels and issue traffic alerts or instruct the IFR acft to turn away from the descending traffic.
Just 'coz we sent them out in the past, beyond the areas that are now Class C, doesn't mean they can't be offered info to do it safely -well, relatively
- in future.
Documents are currently unclear - but if requiring a clearance makes it safer for all, why not? Dunno about CASA having yet confirmed that a clearance IS required, but maybe making this a rule will keep us all alive to argue the case another day - the clearance will not be issued if an IFR or observed VFR is underneath!)