I finally was able to get some custom gas springs made and installed. They work very well. The short story is that I used a company in Oregon, American Gas Springs. I know others have had good results getting custom springs made by other sources, but I wasn't able to find any who would make small orders.

I used 1200N for a final gas spring force. A detailed description of the process, as well as the dimensions and install are described in a document available on Google Drive:

https://drive.google.com/file/d/1oEe...ew?usp=sharing