Dozenalists claim that this would ease mental math, especially with fractions and multiplication. For example, in dozenal math, 1/3 is 0.4, and the multiplication table shows more regularities and is therefore easier to memorize.
Dozenal requires two additional digits, and the society suggests the use of an upside-down 2 and 3.
Their website: http://www.dsgb.orbix.co.uk