Full text search min word length

Hi,

I am using fulltext searches and they are working fine. We have set
ft_min_word_length to 3.

However, some users need to search for two-letter words, and we are not
sure if we should change ft_min_word_length to

ft_min_word_length=2

Does changing ft_min_word_length from 3 to 2 have a large impact on
query response times? What about index size? CPU usage?

Thanks for your help!