So I was thinking of a way to swiss cheese my piston without using a power drill or rotary tool, so I got to thinking...what if I used a lighter, melted the plastic, and cut off the melted plastic that was meant to be removed? So I tried this, and was quite pleased with the results. I haven't reassembled the GB yet to test how it works, but the spring does fit inside the piston. It took me about 30 minutes to get to the point where I got. The piston fit in the grooves of the gearbox and worked flawlessly. I did however have to shape the plastic correctly to do this. NOTE: I didn't remember that plastic can be harmful when burned, especially indoors. Make sure if you try this, you do it outside.