set header style from xml

I would like to set the style of one header column to have padding:0 when I load from XML, how can I do this?

There is no way to set style for one header cell from xml. It can be done only with API:
mygrid.setHeader(“A,B,C”,null,[“text-align:right;”,“text-align:left;”,“text-align:center”]); … _setheader

can setHeader be called after init?

No, setHeader cannot be called after init.