While this is a great little homebrew capacitor, it handles 100 W only because it uses a larger fixed capacitor in parallel. Most of the energy is absorbed by the larger capacitor. When I tried to expand this to more plates, the capacitor arced when running 100 W. The plastic in-between plates acts as a dielectric.  It raises the the electric field between plates. That is not a bad thing, but the air in the tiny air gaps between the plastic and the plates breaks down and starts an arc. The arcing leads to burned plastic. The only solution is to remove all plastic from between the plates. This calls for a new design where the 3D printed parts are an exoskeleton for the fixed and moving plates. See the next project on how to design a multi-plate high voltage RF capacitor. The rack and pinion are replaced by a motor with a lead screw. This is the design I use all the time now.