It appears that Honda put through a different RVD1 doc put through for MY05 (i.e. late 04) Euro as compared to the original MY03 Euro.

The MY03 RVD only has 16" rims listed, whilst MY05 RVD has the 16s and 17s listed.

MY03: http://rvcs-prodweb.dot.gov.au/perl/...2003103116.cmd
MY05: http://rvcs-prodweb.dot.gov.au/perl/...2004154723.cmd

From my understanding, this means that officially, the largest wheel on a MY03 Euro chassis was 16" wheels, which means that your 18" is two inches larger than biggest stock (complianced) size. If you had a MY05 chassis, then the largest wheel offered stock (complianced) was the 17".

Not sure if you can argue the fact that the two chassis have minimal (if any) differences. My understanding is that officially, these are complianced as two different chassis, as the MY05 RVD1 doc is submitted separately from MY03, rather than as a correction.