Revising/adding General Product Posting Groups

If we were to expand our General Product Posting Group by adding a new group and change some of our existing Items and/or Resources to the new group, would it affect any of our open sales orders that have NOT been shipped in Nav? Will it affect items/resources that HAVE been shipped but not yet invoiced? If it will, how could we add/modify the existing General Product Posting Groups with limited issues?

All PG info is copied to SO Header/Lines upon creation, so no effect on them - lines will contain those groups, which were set for I/R at that moment.

However, if you change GL Acc settings for some PG, these will be fetched at the moment of actual posting.