I just remembered I did it before for MQ to use Manage Transport Properties/Headers Assertion to set the custom message descriptor for the message.
You may try the same to JMS property -- add a header of "JMS_TIBCO_PRESERVE_UNDELIVERED" to the JMS message.
Another thing you can try is here (I believe it should be the same as adding header)
sorry, I don't have env to verify, you may try the above 2 options and advise if any of them would work for you.