Wow, did it really get that low? I played with SD during the initial days, and I know there was some strides then to get it running on 8gb cards and maybe squeaking through on 6gb with a smaller image size (like, 256x256px).
Can you generate reasonably large images on 4gb now, with just a higher wait time? I was never sure why it wasn't simple to just shuffle bits in and out of main RAM but I guess the model themselves are mostly big binary blobs that are hard to split up?