> I see no way that a plugin can suggest URLs to the main 
program.
> Should I just overwrite adr and fil that are passed in to
> check-link?  That doesn't sound healthy:)

If the link is passed to check-link, you can without 
problems patch the link (this is the hiddenn purpose of 
check-link, actually) and assume 512 bytes room for the 
link.

Similarly, it is "legal" to patch the destination name in 
the save-name callback.

But if no link is passed to httrack, this is more a parsing 
problem, and this one will be MUCH more complex to handle..