[rt-users] are Attachment records necessary?

[Jim Rowan]

You might want to look at one of the RT import scripts for guidance.  I
did something quite similar to what you are doing and found that using
it as a basis for my custom import script was far more effective than
writing it from scratch.  (Notwithstanding the fact that I did end up
replacing most of it.)  You can definitely use the existing classes to
create things with specific ticket numbers.

Jim Rowan