Hi Mark,
if you see AddSOAPHeaderBean in the blog, it will add any element, my view is that it will also add element with attribute, it might not come as
<async expectReply="false" xmlns="http://schema.store"/> in header
but till come with its own header element
<customheader>
<async expectReply="false" xmlns="http://schema.store"/>
</customheader>
on other hand SOAP AXIS should also work quicker and gives lot of flexibility.
regards
Nisar