You cannot use "any sheet metal." Compliance requires precision. Here are the top materials used in SR2 R66 skins:
The ECE R66 standard is most common on Super High Deck (SHD) models. Skins for these include detailed textures for the under-seat luggage compartments and high-mounted passenger windows. How to Install an SR2 ECE R66 Skin in BUSSID sr2 ece r66 bus skin
Why is "SR2" appearing with ECE R66? Many fleet operators are now dealing with that were built before R66 was enforced in their region, or they are converting standard buses to R66-compliant school buses or emergency vehicles. You cannot use "any sheet metal