If I understand you correctly, your words ”set my own-preferred bar lines” mean “set my own-preferred measure widths” - right?

My first guess:

Document Options > Multimeasure Rests

De-select the option {Update Automatically}.

Even if this is an option about Multimeasure Rests, it affects all measure widths.

You do not need the option {Update Automatically} when you have finished entering the notes (in Scroll View), and begin working on the layout (in Page View).

{Update Automatically} will break a multimeasure rest when you (from Scroll View) enter notes into the multimeasure rest.

Peter, you nailed that one, for sure! I knew there was something in Documents Options I needed to uncheck. I am an old, big band copyist, and I still carry over from my pen and ink days, writing four bars in a line. I hate the way Finale defaults in a line with a three-measure rest and one measure of notation, with the notations measure being way out of proportion when compared to the 3 bar multi measure rest. 

Thanks for solving this issue for me. 

As Peter said, enter your score in Scroll View. After you have them in, switch back to Page View, and take care of formatting. Trying to do it as you go is asking for frustration.