So, if I have a file (.stl) in 1:100 and want it in 1:87 how do I do that?
In your slicer (Cura, Slic3r, or whichever one you are using), just select "Scaling" and enter this value:
100 / 87 x 100% =
114.9%Make sure you do this for all axes (uniform scaling, it should do it automatically like this by default).