I’d go one step further than scotlandx and suggest that your parking space as shown on the strata plan extends from floor to the underside of the ceiling above it. In effect you own that space, so you as an individual are entitled to all of it, unless you lease or sell it to someone else. That may present problems, I’m not very familiar with stack parking but if it has to be attached to common property then load capacity would come into it, also the potential for increased fire loading should a fire occur would need to be considered by your council.