inspired by hooked on pinballs spinner mod for met pro i did the same for my GOTG. The layouts of the machines are similar and the mounting spots are about the same, it does requires notching the orbit plastics , they are hooked to the # 2 hadron target so the first spin will spot you that hadron and you get the hadron sound when they are activated , not a big effect on scoring . the hooked on pinball thread has some good referenced on mounting etc. I mounted mine a little higher in the orbits to keep from obscuring the character insert

https://pinside.com/pinball/forum/topic/new-pinball-hkd-metallica-pro-with-add-on-spinners

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not sure what you mean , the matrix wires are soldered to the the spinner switch lugs in standard fashion , the alligator clips go on the 2 lugs of the hadron target ( I used # 2 as it gets hit all the time to minimize the spinner hits completing the hadrons)

I used my bench grinder works really well for controlled shaping of plastics , others had use hand held dremels

Yes if you are stressing about drilling a hole in a part of the Playfield that is completely hidden by plastics this mod is not for you