Yes.
You can set the order of fields using the "order parameter in the fields.ini file.
eg
[field1]
order=2
[field2]
order=1
In this scenario field2 would be shown before field1.
To set the order of relationship tabs, you set the action

rder attribute in the relationships.ini file
e.g.
[relationship1]
__sql__ = "select * from ..."
action: order=2 (there's not actually a space after the semi colon.. this is just to beat the smilies)
[relationship2]
__sql__ = "select * from ..."
action: order=1
In this case the relationship1 tab would be displayed after the relationship2 tab.
Best regards
Steve