so:
1) you are probably running an old version of the image, which uses Pd 0.46 and it crashes.
2) on a more recent version, I tried it: it runs, but you get dropouts. It seems that 2048 is the largest size I can run without dropouts. However, be aware that - as mentioned above - you would not be fully using the CPU, so you would not be able to do much with the CPU besides the FFT itself.
