Hi
of course the extension doesn't come with a plugin for sh404. it uses the standard joomla route.
Several large extensions comes with an sh404SEF plugin. As you didn't specify the extension involved, that was a valid suggestion.
is there a way to try your extension? so if necessary you could also quote for us the developement of the plugin (you could give us access to your online demo where we could try it or a 30day trial to try on our testsite).
We don't have an online demo. Such demo would be of limited use, as an extension like sh404SEF is not something you can really validate in 30 minutes or so. Unlike many GPL-licensed software provider, we do refunds (see FAQ) so that certainly is your best bet here.
Rgds