Hi @sixfootjames,
Just so you know. This is not Elliot, we are here to help him with his super popular plugin. 🙂
I would consider doing this using jQuery and AJAX. You could use ACF to generate your original select and a blank select.
And then write some generic PHP to accept an AJAX request with the selection and then return a data set to populate the second select.
IMO, this would make for a better UX.
