After many hours of trying to figure this out it appears there is no way to do this with the code that Blocs currently creates. Im going to have to look at an alternative Form posting script for use with October CMS so this may take a while to test and figure out.
In the meantime I have created this knowledge base post that offers a manual work around. It's relatively straight forward but does require a little hard coding (not meaning complex but meaning rigid), which is not ideal.
So apologies again that this isn't as simple as I want it to be, but I will continue to look for a permanent solution.