# Minimum side length of fission structures.
    I:fission_min_size=1

    # Maximum side length of fission structures.
    I:fission_max_size=24

I left it at the default configs of 24.

Will look into it - I suspect that the issue is just that it is checking one or two blocks too far rather than there being no size limit at all.

Sorted - was just checking one block too far :)