The design phase of the CryoAC DM for the ATHENA X-IFU has concerned numerical simulations to exploit different fabrication possibilities. The mechanical simulations have accounted for the peculiar detector structure: 4 silicon chips asymmetrically suspended by means of 4 microbridges each. A preliminary study was performed to analyze the response to acceleration spectra in the frequency domain, shocks and time domain random displacement, prior to a real vibration test campaign. EM simulations to spot unwanted magnetic fields have been conducted as well. In this work we will show the latest advance in the design of the new detectors, showing the main results coming from various simulations