m yet
      still provides an extremely low probability of undetected errors.

      The modulo on unsigned long accumulators can be delayed for 5552
      bytes, so the modulo operation time is negligible.  If the bytes
      are a, b, c, the second sum is 3a + 2b + c + 3, and so is position
      and order sensitive, unlike the first sum, which is just a
      checksum.  That 65521 is prime is important to avoid a possible
      large class of two-byte errors that leave the check unchanged.
      (The Fle