I would get some cheap white fabric and try things out. Just a flat bedsheet from Walmart will do fine. It's not going to be great image quality, but that's not the goal here. The goal is to try the larger sizes and see if you actually do hate them.
I use a X590 (RS440) on a 161" screen and I sit about 15' eyes to screen. It's fun. But, with about 10" of diagonal for each foot of viewing distance, you really aren't doing much different than what I am. I can definitely say that the added screen size is something I enjoy. But, with 2.35 content, it's the same issue you are dealing with.
Be aware, there are other options for masking other than purchasing a motorized solution. There are magnetic maskings options for screens which just snap into place and cover your current screen white areas with 2.35 material. You can also make masking systems yourself. Interesting project if you are a DiY type of person who can handle a screwdriver and do some sawing and similar type of work.
I personally have a real issue with 2.35 and the zoom method. I mean, if you are happy with a 130" 2.35 image that is zoomed in, why not just go ahead and get a 145" 16:9 screen and call it done? If you hate the white leftover screen with 2.35 content, then figure out a masking system that works for you. Lots and lots of fun ways to do things, but I think I would start by trying a different screen size. Go bigger and see how you like the 2.35 content at maximum width. If you hate it and decide you like what you have, then call it a day. I know that at 161" I don't crave more brightness really, so I'm not sure how much you are looking for other than with HDR content which is never really going to be bright enough with front projection I believe.
Go big, give it a try, then it will help direct the rest of your pathway.
Not sure new material will be a tremendous difference, I would have a really hard time suggesting that as a good idea.