The M2B was a mid-engined rear-wheel drive monocoque design, monocoques having been popularised by Lotus's 25 of 1962. Influenced by his aerospace experience, Herd built the chassis with Mallite, a material that had originally been designed for internal panelling in aircraft. Mallite is a composite of balsa wood bonded between two sheets of aluminium alloy that is much stiffer than ordinary aluminium alloy, a useful characteristic for a racing car. However, the material proved to be difficult to bend into the curved shapes needed and so, whilst the M2A prototype was made entirely of Mallite except for the steel bulkheads, on the M2B it was utilised only for the inner and upper skins, the remainder being aluminium alloy. Mallite was also complicated to repair after crash damage. Its use did mean though that the chassis was the stiffest then built for an open-cockpit car, with torsional rigidity of nearly per degree. Glass-reinforced plastic bodywork covered the nose, cockpit and engine. Fuel was stored in rubber bag tanks situated within the moncoque.