Currently the following is the only method to set up a "private match" in swbf2. Up to this point it has only been tested and proven to work on HvV but i though i would share the method with the community.
1. Create 2 groups of 4 players each
2. Make sure both of the people looking for the games have a method of communicating with one another
3. Have the game searcher of party 1 start counting up from 1 to 3.
4. On the count of 2 party 1 searcher must hit search
5. 1 second later on the count of 3 the searcher for the other party must hit search.
After a few seconds both groups should be in the same lobby
I hope this will help everyone out, this method was shown to me by Fanboy Features on YouTube and they use it in their streams. I have only seen this work on PS4 but may be possible on the other platforms as well. Sorry if thos doesnt work for you. I havent tested this myself yet but UnforeseenHenry from my team has said that he and some friend have repeatedly made this work when they play HvV. If you find anything else id love to hear it. Thanks everyone.