20% or 100% infill should not make any difference so close to the center of rotation. Propeller balancer from MP Jet (Art No.: 4160), some plywood and screws. Two M6 screws I have countersunk in the center to hold the balancer. Screws mounted into threaded holes in the wood. Allows to give it some tension, so the blades rotate easily and do not fall down. The 17.5 mm outer diameter should give it a tight fit in the blade center tooth-wheel.