Hey Steve,
Have you come up with a solution?
I burned a lot of time trying all sorts of combinations to integrate a WP form with NetSuite and never got anywhere. In the end, I had to just develop my own plugin (using curl).
While developing my plugin I had every intention of writing it in a way that would easily apply to other configurations so that I could publish it and give it away for free. Unfortunately, time wasn’t on my side so it’s very much tied to my specific use case and NS forms. I’m hoping to come back around to it at some point though…