Thanks for the input Rick! In my version of Architectural 2018, I am selecting "Edit" from the main menu, then "Default Settings", then "Floors and Rooms", then "Current Floor", and then "Edit".... at this point, the only default selection options that I see are for "Ceiling Finish" and "Floor Finish". I have checked both of those boxes, but it hasn't altered the Floor Structure value of 4". I am probably missing something. How are you getting to the "defaults dbx" that you mentioned?
Thanks and best regards,
Will