Transit Bus Interior Walls

[Metatron]

To the transit/shuttle bus people. Since the walls are mostly window with little opportunity for insulation I was planning an just building over the existing 1/4" cardboard type of interior wall material. However it is falling apart and am tempted to rip it down but don't want to create more headache than necessary. What do you all do? leave it or remove? Is there metal under it or open ribs? 01 BB TC2000. Thanks for any info.