Hi Eric, have you ever tried GRS-Thermo- Loc Sticks? They are used in the jewellery trade to hold rings etc while you work on them. The product is also good for molding shapes etc and you can vac over them. The sticks become pliable in hot water and set up at room temperature. You can use them over and over. Just thinking you could have used this stuff to push through the window opening and then trim to shape and use it as a mold. I have used them for years in the ship modelling to make multiple shapes. Just remember to pop it in the freezer before you vac form over it.
Now that the opening had been modified, I needed to work out how I was going to make up a new clear part to fit it. I am yet to work out exactly how I will do it, but I have started the process.
I carved a block of balsa to fit the new opening. The majority of the window is flat, so it wont be too much of a problem. It is the compound curve of the upper surface that will be. This will allow me to hopefully plunge mould a new window. Failing that, I will buy a vac form machine. I selected the end grain to carve, and have wicked thin superglue over the surface, filling the grain and allowing me to sand and polish it to a very smooth and hard surface.