Two new execInsts (PostOnly and PostOnlyReprice) are now available for prod orders. PostOnly is an exact synonym of ParticipateDoNotInitiate, orders will behave in exactly the same way if either is present (any order that would execute immediately is instead cancelled). PostOnlyReprice will never execute immediately, similar to PostOnly. However, instead of cancelling, it will find the nearest price on the same side of the book that is available to post on, and will post there instead.
For example, if the top of book is 97.3 - 97.7, a PostOnly to buy at 97.9 will be cancelled. A PostOnlyReprice to buy at 97.9 will not cancel, but will instead post with a buy price of 97.6, so the top of book will now look like 97.6 - 97.7.
In the meantime, if you have any questions please contact Support.