Hi @amsross
I am yet to look at ACF and the XML rpc interface, however, I do believe it is possible to save the repeater field data.
Take a look at the repeater field docs page. On there you will see an example of how the data is stored. I think you could post across all the sub field / row data as separate custom field values in the correct format (see repeater field docs) and the repeater field should work with the data.
Give it a go, and let me know how you get on.
Thanks
E
