I knew there was something wrong with this window opening, but I couldn't put my finger on it until a few days ago. I didn't get a chance to work on it until my days off.

The window opening did not angle upwards at the bottom steeply enough and it didn't line up with the #4 window around the front of the airplane.

All I did was cut another lower sill and angled it upwards with support underneath from a small length of wood strip.

Found some plastic in the shop hiding in a dark corner and was able to actually bend this stuff around the opening without any trouble. It's not plexiglass, but some really brittle, thin plastic that might be used in a poster or picture frame.

Here is the before photo:

And the after photo. I still haven't decided how to finish the trim a little more realistically looking, but I'll get to it.