New product qualification with ETO sterilisation (Validated Process)

Hi there,
We do ETO sterilisation (Validated) for our products, if I want to introduce new product, how can I demonstrate that the ETO sterilisation process is effective at the most difficult to sterilize location within the new product packed in the manner in which it is presented for sterilisation?
How can I show that the process challenge device presents an equivalent or greater challenge to the process than the product bio-burden?

• We have already conducted sub-lethal cycle with worst case product and it was passed,
• We also conduct half cycle validation every two year.
• We conduct Annual review of Cycle Validation every year.

What else do I need to do to show ETO sterilisation process is effective at the most difficult to sterilisation location?
Thanks for your assistance