You're gonna have to work with me a bit here Chris as I haven't built one of these before so I'm working by what I've seen at the field and am reading in the manual, OK?

First I am assuming that you are saying that you can't get the plastic screw/nuts to install properly on the studs that are mounted in the vert fin and stuck down thru the horizontal stab. These screw/nuts are not supposed to go up inside where they will be unseen.

Is the front hole simply too small and if you enlarged it slightly would all be OK?