I got the window sections all tacked together on the window for "close" spacing of the window edge to the roof sections. Laid it into the original opening and you can see how much smaller the new opening will be. Also, how much the hole varies from top to bottom. Closer on the bottom of course because that dimension didn't change from factory. View attachment WP_20150926_015.jpg
Here's a good view of how much narrower I had to make the hole for flush mount. View attachment WP_20150926_018.jpg
I left extra material from the donor parts to overlap the factory window hole. Then I can take a cut off wheel and cut to match the window opening. View attachment WP_20150926_019.jpg
View attachment WP_20150926_032.jpg
I am glad most all of the interior window trim is metal. I have the donor pieces for that also so I can modify those to fit the new window opening.
The flush window treatment looks so much smoother. I like it a lot.