You will also loose compression ratio with stacking gaskets by increasing cylinder volume. AKA loosing your squish factor. I'm telling you if its barely bumping , find out where its bumping per the instructions above and just relieve the piston (grind or sand a pinch from it till it quits hitting). The Millwright trade (precission machanics) use this method. They actually have a blue washable type ink they use for this. But you can use any coloring that will do the job. Its gotta be kind of thick so it won't run everywhere. It just colors where its making contact. I swear Best, Cheapest and most likely quickest way to solve your problem . Unless its hitting in a ring fashion like that photo above. Then you will have to use one of the other methods of getting around this problem of yours.