The documentation on the methodology to set new defaults for ViVA is not accurate.The defaults can be placed in your .cdsinit file and must be preceeded by lading the ViVA context as detailed below.
; ViVa default fonts to Clean
; Added from Wayne Ingram's note on 7/24/2013
; If customer is setting font related cdsenv variables in .cdsinit (via envSetVal API),
; there's a requirement to load the 'viva' context _before_ any envSetVal call is made.
; This can be achieved by the following in the .cdsinit file:
envSetVal("viva.graph" "titleFont" 'string "Clean,12,-1,5,55,0,0,0,0,0")
envSetVal("viva.axis" "font" 'string "Clean,12,-1,5,50,0,0,0,0,0")