I didn't see anyone else ask this yet, but would you like to divulge the location you are interested in checking out ShellyGale?
Regarding the speculation that SS may be close to home for BRE as per 1996, anything is possible but I'm not so sure. If the MO was the same as with JR and CG (i.e. dumped in bushes very close to isolated, low-traffic roads), then it's almost guaranteed that SS would have been found by now. Bushland close to residential developments is far more likely to be frequented (for one thing) by explorative kids in the neighbourhood, making 'hideouts' using branches and that kind of thing.
If it's the same BRE who was playing indoor cricket at Canning Vale back in the mid 90's, I wonder how familiar he was with the area between that and his line of work? Just past the industrial zone, Canning Vale was still largely bushland, hobby farms and nurseries back then. Jandakot however still retains a lot of undeveloped land over the water mound, and in semi-rural areas such as the kennel zones.
On the other hand, if SS was dumped in a similarly isolated location as with JR / CG, she would be within meters of a road, whether semi-rural or in one of the nearby national parks. How likely is it that an unburied body, covered by foliage could remain undiscovered so close to a road for two decades and counting? Could natural processes such as growing foliage, moving topsoil and animal activity have long since ruined any chance of stumbling across any bones or clothing fragments after all this time?