From my simple understanding, it sounds like fixed spacers; that is, ones with studs fixed to them; are the way to go.
I can see that if you fit spacers larger than 7mm, you put a stress on your STOCK studs because you essentially use 7mm less of the stud which, im no engineer, could potentially cause the wheel to get damaged/out of balance/break/fall off.... something along the lines.
I think the reason why there could be confusion in the law, and I HAVEN'T seen the modification sheet made by QLD GOVT, is because, to make it safe they need to make it clear the easy way and say they are illegal.
To me the fixed spacer idea, as long as they are of good quality, is great. To a certain size of fixed spacer, i can not see why using it would be bad at all, and of course as long as a mechanic/engineer sees it as safe.
=)