Personally, I think anyone who says they notice a difference from the clocking of the spark plug in a china girl engine needs to have their meds adjusted. Adding compression by filling the chamber with a projecting spark plug iffy at best, even in these weak kittens.
In any other motor, it's a good way to explore the wonderful world of pre-ignition.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.