Adding a level to the hierarchy

I'm wondering if there is a way to add a level to Texinfo's hierarchy, so
that there is a level below subsubsection. I'm including files
using @include, @lowersections and @raisesections, and occasionally I
"bottom out" and end up with a partially flattened hierarchy where there
should be a fifth level. The content is very hierarchical in nature, so
retaining this structure is very desirable!

Thanks!

- Benjamin Kalish