db5: simplesect with two section ancestors

Is it valid DocBook 5 to have a simplesect element with two section
ancestors (ie, section > section > simplesect)? It seems valid to me
from the description on docbook.org, but XMLMind doesn't seem to allow this.

(By the way, the rationale is that I'd like to have a short section with
a title such as "To do x:" followed by a short procedure. 'Section'
seems to overwhelm such a heading with section numbers; and as there are
no nested sections within, 'simplesect' seems more semantically
appropriate.)

Thanks,

Brett