Sounds like you're all set! But for future reference, you can delete them by simply clicking/highlighting the incorrect margin (probably from bad XML info) and clicking delete. Or you can highlight the part, click on identify part features, and scroll through the selection #s until the incorrect margin is highlighted and click delete.
To redefine the margins, when you're in the same menu (identify part features) just click on the margin or just below the margin on the inside of a coping. hyperDENT will do the rest and automatically define it for you.
If it's a really rough STL file, we have a new, super-easy way to manually define the margin where you click a point to start and then click a few additional points around the coping - the whole time a proposal from the last point to the current point tells you if it's exactly where/how you want it. If not, then choose a point that's closer to your last one and it'll self-correct. I'll have to make a video soon because it's really slick!