CiviCRM and Layouts

I have gotten a basic Drupal7 -> Backdrop migration done, and am fine tuning the site.

Layouts is a new thing for me. I've set up the site to use single column Boxton for administration, and Moscone as the default layout for everything else.  This works well for doing administrative work in CiviCRM for our staff.

In case you don't know, CiviCRM isn't administered via backdrop administration, so the Boxton theme isn't involved here.  Also, CiviCRM administration uses, basically, a two column layout; a side bar for some useful blocks, and a main content area for the data.  So for this, Moscone is perfect.

But for public facing purposes such as filling out a form or making a donation, there are no blocks involved. In the Moscone layout, the form is in it's proper place in the main content area, but the sidebar is completely empty and using up valuable screen space.  And the form is not justified to the left border to the div, nor is it centered.  It just looks whacked.

How do I deal with this? I am aware that this is a bootstrap design, with that sidebar getting an md-3 class to specify width. Basically, I want that width class to disapear - or the div to disappear - and the main content area to become md-12.  Or at least that's how my thinking is going.

I couldn't be the first one to try and solve this....