I need to know more about this failure.

a) Does the file system block size seem to affect how large you can
make the partition?

b) If you create two partitions, one 8GB (at the beginning), and one
1GB (at the end), and newfs both of them, are they both okay?  Does
doing I/O to the second partition corrupt the first one?

This will help me assess what sort of bug it is.