Adding window into the Door

The porthole is secured closed by two hand star nuts that are about 1 1/2" in diameter.  They fit between the screen door and the hard door, but only barely.  They do press against the screen, but not enough to cause a problem.  

Marine portholes swing up to open and the bolts and hand star nuts drop down out of the way.  You can buy screens for them, but it really isn't necessary since the screen door functions as a screen when in the open position.

One of the biggest problems with window flange is about just long enough to fit through, but just barely.  When you tighten down the ring flange which goes around the outside of the window, it is just barely covers the window flange, leaving a flush surface, but you end up compressing the door a bit to get a good seal.  After installing mine, I developed a horizontal crack on the surface of the inside of my door centered on the porthole.  It doesn't hurt anything, but it indicates that there was some stress that had to give.  

If I had it to do over again, I'd have bought the window from the supplier mentioned in this thread, but at the time, I didn't know about them.