Hi,
please check the following performance improvements: https://github.com/fuzzylite/fuzzylite/commit/2661878364685e17a2fc286e41b6d647066722b2.
However, have in mind that I need to undo many changes performed in commit https://github.com/fuzzylite/fuzzylite/commit/33119032d12e3337cbe8efa984086ce7379f1081, where I chose some methods over access to properties, which have had a significant impact in performance. I am still working on this.
Also, I am making these changes available for version 6.0, not for 5.x.