Sorry no one else has taken a look at your files. @WillAdams, any thoughts on the original problem here? His Carbide files look fine to me. Still not sure how the actual measurements came out for you though.
Here's how my cut turned out today from the Fusion 360 design above. Pretty good fit, although I had to sand where my tabs were. It's not perfect because I still screwed up the work holding on my box lid and it got slightly messed up. But it will work for a simple project. I'm going to probably seal and finish the lid and box before I V-carve something into the lid. I had to sand the lid a little on one side / edge, because of the work holding issue, but if not for that I think it would have fit very well. Not loose, but not a press fit either.