You are so lucky to be able to grow this gorgeous tree! Its flowers are lovely. *jealous* :-)

According to this website -
http://www.agroforestry.net/tti/H.tiliaceus-beach-hibiscus.pdf

"Living fences
A hedge of beach hibiscus planted on 1 - 2 metre (3.3 - 6.6 feet) centres can be trimmed regularly to provide a dense living fence."

It goes on to say -
"Use as living fence, hedge, or visual/noise barrier
Beach hibiscus is frequently used in urban environments
as a hedge or privacy screen. Regular pruning to maintain appropriate size and a groomed appearance is necessary.
Maintenance requirements
The unruly habit of the tree can be tamed by regular pruning 1–3 times per year into a hedge or specimen tree, or by training the branches on a trellis or pergola. Otherwise, the tree requires little attention once established."

And it also says that the roots are invasive and can cause problems in urban areas.

Happy growing!