Public transport between Navala (via Bukuya) and Sigatoka?

I can't really get sufficient information about public transport between Navala (via Bukuya) and Sigatoka. I would like to do 'the rough road' and not the 'Kings Road'. Are there busses between these two places? And if 'yes', are there more busses a day?

I'm 100% sure there are no buses through the interior linking them.
Not even passenger trucks, as Navala people travel out to the north, not down south. And market trucks heading up the valley from Sigatoka don't reach anywhere near Navala.

Years ago we did the trip by car - I'm certain no buses go that way.