How do you form furring strips if your boards run front to back?

[Michael_Grumbach]

We want to use 4" or 6" boards for wall and ceiling coverings.
We want to add furring strips to increase the insulation thickness and create a thermal break.
But how do you attach the furring strips which normally run the length of the bus and also have wall and ceiling coverings that also run the length of the bus?
We could mount furring strips all along each bus rib, but then we would be cutting short squares and drilling lots of holes for attachment screws.
We could attach the furring strips to the sides of the ribs, but we would be losing insulation and the nice curve of the ceiling.
Maybe we could use thinner flexible strips for the ceiling and apply them in multiple layers?
Maybe there is another material, other than wood, that we can attach to the curve of each rib, which follow the curve, not crack and provide an anchor point for the ceiling boards?
Any suggestions would be greatly appreciated.
Thanks.

[Michael_Grumbach]

I found this video, but I don't know what material they were using.
It's surprisingly bendy.

https://www.youtube.com/watch?v=37dDG1dDuWg

[somewhereinusa]

Make your furring strips out of plywood. On the back side cut a strip about 1/4 inch apart through all but one ply. It will then bend pretty sharply. When you mount it put a bead of something like liquid nails on the side with the grooves. It will squish into the grooves when you pull it in with screws.

https://www.thebasicwoodworking.com/...-bend-plywood/