My SSD has 40 GB free space, i have my lights, flats and bias files on an external USB3 (1.5 TB) hard drive, so i can not stack 157 lights, 30 flats and 150 bias frames with this setup. I think you should clearly indicate the system requirements, to compare things, i can stack any number of lights, flats and bias in DeepSkyStacker with 4 GB RAM when there is enough external hard drive space. Maybe i should set the APP working directory pointing to the external drive?