FYI, the 1/8” router bit I had actually turned out to be an upcut, but a number of shallow passes worked brilliantly. I have an INCRA lift in my table and was able to creep up on the depth to leave a very small amount that could be removed with an exacto. It left a very smooth suface that just needed a wee bit of sanding to get a great fit without any gaps. May end up being my go to method.