DMG mounts but does not auto-open
Here are a few online guides to creating auto-opening DMG files.

From the first guide by Bill Bateman, step 23 seems to be the key:


  Click Convert on the toolbar. Enter a new filename and make sure the
  image format is compressed.  Click Save.  This creates a new image.


Another guide (via this post) has a bunch of information. The info regarding the auto-open piece is here:


  But we found that the .dmg doesn't always open up its window when
  mounted. This “autoOpen” utility solves that problem:
       http://autoopen.nibfile.com/


One of these two guides should help you set up the auto-opening DMG.