How are you making miter splines? I use a 1/8" saw blade to make the slots in a miter spine jig I made. Then I plane down or resaw strips to be used for the splines. Scrap pieces if I have some. My planer only goes to 1/4" so I made a planer sled to allow me to go thinner. I take tiny passes checking after each pass for fit in the spline slots. Then cut the splines on the bandsaw. Somewhat tedious. Curious to other methods.