What I believe is most important is matching the address for DCC GET trust works with all the $address modes including 5.

This might mean matching against both $ial($nick) and $mode($nick,5) if they are different - I doubt that this would introduce any backward incompatibilities or security issues.

In the mean time I can switch my own code to use $ial($nick) if you can confirm that is the one which will work.

Many thanks.