We did a similar style case a week ago. We actually scanned the entire arch and made one big overlay style bridge.
setting the margin at the gum line, you need to make sure you have a 100% clean impression and get rid of all the little blebs and what not, clean anatomy. I selected in the case creation all the teeth that were going to be covered, 1st molar to 1st molar. For sectioned teeth on an unsectioned model, set them as full contour crowns then selected all of them and applied a bridge with none as the connector. Then scanned, set margins, die spacer added to the extra spacer for more room then set the teeth and played around till happy. Cut out of A0 PMMA seated and cleared the occ. This is one way of doing a removable smile non prep that is. If the Dr is going to open then bite then it gives you even more room to achieve better esthetics.
Another trick is do not select the full contour crown when you create the original case, select all the teeth and set them as veneers. This will actually allow you to scan the arch and then just simply number the teeth and move on, instead of having to section them like full crowns. The only thin is before you design, go back into the case and change them to crowns and bridge them. It will say you have changed the product would you like to rescan, simply say no cause your design is still Zero then just CRTL-D or right click model and whalla you have a true unsectioned model allowing you better inter proximal space. But with this technique 3shape is totally lost on margins and you will have to clear and manually mark each tooth, very very time stacking but it works great once you get the hang of it. This is a work around I figured out when trying to do a diagnostic wax up of veneers, I changed them to crowns and in the smile composer i got a much better preview then with the veneers. A little something I rubbed into their face at LDW! LOL
Sevan