OK, after disassembling the entrance door, I have a much clearer project now.
Two options. First is cheapest and easiest. Since the blinds have been on there, we have NEVER opened them. The rod to do so broke off, and i never put it back on. Less noise. So I dont need another external roll up shade. So this would be a great solution -
https://www.amazon.com/Kohree-Sunshade-Blackout-Protection-Waterproof/dp/B07X5WMM65/Leave it on there 24/7 except for the rare times we need to see out.
But hey, why not shoot for the top? Get a little crazy?

This is going to be the replacement window -
https://www.amazon.com/AP-Products-015-201512-Upgrading-Window/dp/B01MRRNQNP/Hight wise, it matches the cutout there now.

Unfortunately, the cutout is 1" too wide.

I can see having a flat adapter plate made from .063 aluminum that would fit under the frame, and cover the reveal on the edges. The plate and the added sealant would HOPEFULLY still be in the thickness range for the window to work. I feel it will be, this from the install instructions: (found here:
http://approducts.net/PDFs/instructions/slimshaeinstallFINAL.pdf )
Note: The installation screws are designed to bottom out in the frame. This prevents over tightening and ensures a proper seal of window and frame to prevent possible leaks.
I think that it will allow me to be a bit on the thick side and have proper screw engagement.
I plan on re-making my inner panel anyway, so I can correct the window opening then. For others that wish to replace the window only, two such adapter rings would be needed. Paint them black, you would never notice them.
If this works, I will be sure to keep all my notes so other PC owners can easily upgrade to these windows. Maybe have several adapters cut at the same time and sell parts.
Going to order the window to get it in my hands, then go forward.
