re: The part in which the 3M corporation pays me well for massive blue tape sales. [I Wish]

Steve, you are absolutely right.  You can end up with some that are shorter.  When that happens, you don't sand.  You want to mix and match with your over-180s to come up with a nice fit.  This is one of the advantages of making several of these at once.

Another quick fix is to simply cut one extra triangle another degree to so wide.

But after making dozens of these, I almost always end up with sides that are greater than 180 and have to be sanded back.