. . . plotters, so they're extremely accurate . . . m

- using a plotter sounds like a plan. You also need a medium such as mylar with uniform characteristics; fiber-based media have a grain.

Even Mylar may not be as stable as you need, it still changes with changes of humidity and temperature, it's just more predictable and the changes are reversible - you can find the data on the web - so if necessary you can use small changes temperature to restore the original dimensions.