After suffering from serious problems in the course of the SiC 1.5m M1 manufacturing, the existing design of the M1, it's cell and the associated mirror cooling system was investigated in terms of modification efforts to be compatible for a different M1 substrate (Zerodur). The analysis included the system requirements, the M1 design, the M1 support system, the M1 cooling system as well as the M1 cell. The investigations resulting in a modified design of the above mentioned system. Driven by the choice of material, different requirements became design driving factors. The consequences on the detail design of the M1 Mirror as well as on the support system and the cooling system are presented.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.