The current rating depends on the cross-section of the conductive area. It does not matter if its round, square or oval. Just the conductive area, like in mm^2 (squared). If it has a hole in it, that hole gets removed for not being conductive.
If you want higher current rating you could use a solid copper conductor. For the same cross-section the solid wire will conduct more, around double. But then instalation is fixed, like for a printer which has the bed completely stationary in all directions.
If you want higher current rating you could use a solid copper conductor. For the same cross-section the solid wire will conduct more, around double. But then instalation is fixed, like for a printer which has the bed completely stationary in all directions.