Thank you for your post.
I'm unfamilar with any CAD viewermapp on the iPad. I'm also unfamiliar with the .dwg file type, but using my favorite browser search engine, I see .dwg file format originated in the Interact CAD application but is also used by AutoCAD, and that the .dwg file format is changing with AutoCAD 2013.
Regardless, assuming the file is embedded, you should be able to click inside the Container field and hold down on the file. An Actions window should then appear, and tap "View". If it doesn't display, then tap the icon in the upper right corner (rectangle with a large right arrow) and select the CAD viewermapp application.
Thanks for answer.
I do agree this is what should happen but it does not. Works as described with other files (xls, pages, pdf...) but the dwg just doe snot work even though it does open when prompted from Mail, DropBox or Evernote. It just looks like FMGo does not 'like' dwg files. needless to say that the file is healthy.
I have opened a support request as a bug (#121029-000034). I run FMGo12 on iOS6.
Here is a screen cap of what i get when trying to view