Mock PQ Subkey Test doesn't offer artifacts for "big" subkeys

The Mock PQ subkey offers some tests with "big" keys, which are described as "huge data (unrepresentable as MPI)".

I'm assuming this just means > 64Kib (i.e. > 8KiB). But there are no artifacts for those objects. It would be great to produce those artifacts as well, for testing purposes.