You can increase the 'fuzziness' slightly by relaxing the stemming mode. By default the stemming basically handles plurals.
To relax this you can add the following query processor option:
-stem=3 (by default it is
-stem=2 which will apply if this is present in the query processor options, or if there is no
-stem=X option in the set of options.
See also: https://docs.funnelback.com/15.22/customise/advanced-options/word-stemming.html
Please note that increasing the fuzziness does tend to reduce the quality of the results because the search may includes words that you were not expecting.