140 degrees range of positive stability is good number that would ensure immediate self righting.
What is important is the negative stability curve which is a relatively short shallow righting arm meaning that it will quickly self right. If you wanted to be sure, just fill the mast with foam or seal it to offset the impact of the fully loaded condition. The capsize screen number is well above 2 however its a simplistic ratio whose design has been validated. The Mini 6.5's get pulled to check its self righting abilities. I am not sure if this has been done for the class 5.80 in a loaded state. It would be interesting to see the result if they pulled it over.
The cost estimates that I have seen for a new build is well over 100K, it just makes no economic sense considering what you can buy for 100 grand. Even fully equipped Golden Globe yachts sell for a lot less fully equipped.
Every sailor has their own dream and path they wish to forge, good luck to those wanting to spend so much in achieving the dream.
The offshore sharpie designs seem to becoming more popular, designs like those in the youtube channel wave rover seems like another good design.
There is a designer who specialises in small craft design and he himself is a vid sailor. His designs appear professional and he has full stability data as well issuing CE rating data. Jerome uses all the latest design tools, however his skills cant make up for inadequacies of a small size.
duckworks.com/jerome-delaunay/Bigger is better and might is right, especially when you consider that all it takes is wave size that is half the beam width to roll anything. 5.8 metres is small.. If I was going small it would be something like a Vertue, Folkboat or TopHat. Something small and sensible.