Hi, I've noticed here in Aust. that these superlatives can be misused and still understood. Usually a shorter word [ one or two syllables ] is made into a superlative adjective by adding ..est. Longer words would become a mouthful so usually see 'most' put before . e.g. most beautiful . I think fairest is right. Unfortunately a great deal of common usage is incorrect in formal terms but accepted simply because it is commonly accepted. 'Most fair' does not sound so bad, but is uncommon.