Just sharing my simplified step files for the st20 140 and 280 variant
Based off these sheets.
https://www.alphacool.com/download/datasheet/ENG_14444_Alphacool_NexXxoS_ST20_HPE_Full_Copper_280mm_Radiator_datasheet.pdf
https://gzhls.at/blob/ldb/d/8/3/5/9f908a28bbeb010645ee6a9b201fd674466b.pdf