Programmatic field weights

I am programmatically adding a field to a view via hook_views_default_views_alter(&$views) ... the problem is that this just adds the field to the bottom of the list. I need to be able to programmatically control where the field shows in the list. I do not see any way to use weight for this. It seems that the order is determined simply by the order of the items in the info arrays. Can anyone help me out? What am I missing.