@Jimi007 Ok so I've answered my own question. It was right in front of me
Using the amiberry conf file the options are
default_horizontal_centering
You can use this option to enable Smart Horizontal Centering by default.
Possible values: yes/no
Default value: no
Example: default_horizontal_centering=yes
default_vertical_centering
You can use this option to enable Smart Vertical Centering by default.
Possible values: yes/no
Default value: no
Example: default_vertical_centering=yes
Added the lines and all good