Anyone know if it's possible to flip the starting location of a rectangular DADO route?

You can see in the screenshot, the starting location is in the middle of the longest edge on the inside of the part. Our vertical router slips slightly when machining these, leading to an uneven cut that's visible on the inside of the cabinet. I want to change this so the start is on the other side of the route instead, so this uneven cut is hidden. 

From what I can tell, this isn't possible from the DADO token. There's options to flip the side the gap/clearance is on, and options to reverse the route if it's a single line pass, but no options to control the rectangular route start. I'm wondering if I'm missing something.