How to change default font for auto field detection when 'preparing form'?

I am creating forms in the form builder and am having to change the font type and size for every form because it keeps defaulting to Helvetica and Auto.  Because Im using the auto-detect feature, I can't do the trick where you create one field and set it to the font and size you want and mark that as default. And doing so in one document doesn't seem to keep that default for future documents anyway.  I've gone to Preferences>Content Editing and changed the font and size there but that didn't affect the fields. 

Basically, how do I set the font type and size for the Field Detection feature in Prepare form?