AutoCAD Civil 3D :: Test The Height Of Fill Slope Relative To Daylight Catch Point?

This seems like something that should be really easy but for the life of me I can't figure it out. I even started looking at using the Subassembly composer to create a custom SA but that seems like a ton of work so something that would seem to be a common problem.

I need to provide a v-ditch with 2:1 side slopes at the toe of a 2:1 fill slope. The flow line of the ditch should be 2 ft below the daylight point of the roadway pavement section.  

My problem is that the conditional subassembly seems to evaluate the height of fill directly beneath the attachment point of the conditional SA (pavement section daylight point in my case – “Daylight_Sub” Point code).  Instead I need it to evaluate the difference in elevation between the catch point of a 2:1 daylight fill slope and the conditional SA attachment point (Daylight_sub). If that difference is less than 2 feet, I need to provide the ditch, otherwise I can just use the daylight slope for the ditch foreslope and the existing surface for the backslope.

how to do this? Maybeits as easy as using a predefined daylight subassembly that I'm overlooking?

Here’s my current assembly attempt: 

And the resulting behavior. It is solving the 2nd fill condition when I would like it to solve the 1st fill condition: