Position of Icons in a DMG file

[sd_dave]

I have the following script that customizes a DMG....
The problem is ... contrary to what the script says.... The icons are NOT located at the coordinates specified. The ones that would be along the top
are "close".. the lower/right icons are way off. I also notice that if I change the X/Y of the window in the script the position of the icons change.

What am I doing wrong/missing here? I need to have the icons appear at the specified coordinates relative to the top left corner of the window

tell application "Finder"
tell disk "test_test.dmg"
   open
   tell container window
      set current view to icon view
      set toolbar visible to false
      set statusbar visible to false
      set x to 251
      set y to 220
      set w to 1009
      set h to 612
      set bounds to {x, y, x + w, y + h}
   end tell
   set opts to icon view options of container window
   tell opts
      set shows icon preview to false
      set shows item info to false
      set icon size to 128
      set text size to 16
      set arrangement to not arranged
      set label position to bottom
      set background color to {32639,0,32639}
   end tell
   set position of file "aaa_test01.app" to {25,96}  
   set position of file "aaa_test02.app" to {803,213}
   set position of file "aaa_test03.app" to {585,68}
   set position of file "aaa_test04.app" to {485,388}
   set position of file "aaa_test05.app" to {52,295}
   set position of file "aaa_test06.app" to {792,30}
   set position of file "aaa_test07.app" to {211,51}
   set position of file "aaa_test08.app" to {439,207}
   set position of file "aaa_test09.app" to {823,406}
   set position of file "aaa_test10.app" to {293,391}
   set position of file "aaa_test11.app" to {381,13}
   set position of file "aaa_test12.app" to {214,226}
   set position of file "aaa_test13.app" to {649,443}
   update without registering applications
   delay 5
end tell
end tell