Right now the only way to change the defaults is to edit the aircraft’s config files. To do that you’d navigate to the directory that stores the content (The one with Community and Official folders), find the aircraft you want to change, and then find the “aircraft.cfg” file. Inside of that you’d find fields you can edit and save the file to change the defaults. They’d most likely get overwritten when the game is updated. Having configurable defaults is already pretty high up on the wishlist. Add a vote to this Wishlist topic to show the devs you want it too.