The reason why I chose a card board material + felt is for noise absorption. If you use any type of thinner, stiffer material there may be a lot of vibration. I've been very happy with mine.
2011 E92 M3 DCT
1991 Spec Miata
2008 E92 M3 DCT - KW Competition 2-way / Brembo 365 BBK / OMP ARS racing seats / rear seats delete / GT4 aero / AiM EVO4 data logger / SmartyCam racing camera
2008 E92 M3 6MT
2008 E92 335xi